diff --git a/audit/internal2/README.md b/audit/internal2/README.md
index 5123c60..52509dc 100644
--- a/audit/internal2/README.md
+++ b/audit/internal2/README.md
@@ -48,7 +48,7 @@ next
         } - skip
 5. pass        
 ```
-[]
+[x] Outdated due to design change
 
 #### Medium. _calculatePayment not update collectedFees;
 ```
@@ -57,7 +57,7 @@ function _calculatePayment(
         uint256 payment
     ) internal virtual returns (uint256 mechPayment, uint256 marketplaceFee) {
 ```
-[]
+[x] Outdated due to design change
 
 #### Medium. payable fallback()
 ```
@@ -65,7 +65,7 @@ Must be payable.
 fallback() external {
         // solhint-disable-next-line avoid-low-level-calls
 ```
-[]
+[x] Fixed
 
 #### Medium. Typo in check. 
 ```
@@ -78,10 +78,10 @@ constructor(address _mechMarketplace, address _serviceRegistry, uint256 _service
             revert ZeroValue();
         }
 ```
-[]
+[x] Outdated due to design change
 
 ####  Low? Notices? OlasMech.setUp(bytes) event
-[]
+[x] Noticed, internal storage writing
 
 #### Low? Notices? Karma.sol Uniform approach to location getImplementation() (proxy/implementation)
 ```
@@ -95,7 +95,7 @@ Depending on what they understand better for etherscan. Probably in proxy better
         }
     }
 ```
-[]
+[x] Noticed
 
 ### Low? improvement create2(), due to unpredictability.
 ```
@@ -125,7 +125,7 @@ bytes32 salt = keccak256(abi.encode(nonce, block.timestamp, msg.sender, serviceI
 
 same for contracts\integrations\nevermined\MechFactorySubscription.sol
 ```
-[]
+[x] Fixed
 
 ### Notices
 #### Low? Notices? No issue? initialize and constructor on MechMarketplace + frontrunning (?!) To discussion
@@ -148,7 +148,7 @@ function initialize(uint256 _fee, uint256 _minResponseTimeout, uint256 _maxRespo
 Frontrunning is possible : between constructor() -> initialize() : No issue!
 Changing the storage of implementation has no effect on changing the storage of proxy!
 ```
-[]
+[x] Noticed
 
 #### Low? Notices? No issue? frontrunning initialize() in Karma.sol. To discussion
 ```
@@ -168,14 +168,14 @@ Example:
     }
 Changing the storage of implementation has no effect on changing the storage of proxy!
 ```
-[]
+[x] Noticed, already initialized
 
 ### Notices. Variable "price". Problem of terminology
 ```
 Problem of terminology. Price is usually expressed as amount0/amount1 
 if (amount < price) {}
 ```
-[]
+[x] Outdated
 
 ### Notices. for design createMech()
 ```
@@ -183,7 +183,7 @@ Can be called by anyone, a small limitation is that it is called from the market
 function createMech()
 -> callback IMechMarketplace(mechMarketplace).mapMechFactories[mechFactory] == address(this)
 ```
-[]
+[x] Fixed
 
 ### Notices. Pure? _calculatePayment()
 ```
@@ -193,12 +193,12 @@ function _calculatePayment(
     ) internal virtual returns (uint256 mechPayment, uint256 marketplaceFee)
     -> pure?
 ```
-[]
+[x] Outdated
 
 ### Notices. Low/Notices
 ```
 uint256 private constant FEE_BASIS_POINTS = 10_000; // 100% в bps
 ```
-[]
+[x] Fixed
 
 
diff --git a/audit/internal3/README.md b/audit/internal3/README.md
index 5c3fd22..2188b32 100644
--- a/audit/internal3/README.md
+++ b/audit/internal3/README.md
@@ -20,13 +20,14 @@ Most of the issues raised by instrumental analysis are outside the scope of the
 
 ### Issue
 #### Medium. Make sure that the previous comments (internal - internal2) have been addressed.
-[]
+[x] Addressed
 
 #### Critical/Medium. checkAndRecordDeliveryRate() for native token
 ```
 function checkAndRecordDeliveryRate()
 This is not the right behavior for a case msg.value > 0 and native token contracts.
 ```
+[x] Fixed
 
 #### Low. More Reentrancy protection
 ```
@@ -34,14 +35,14 @@ function checkAndRecordDeliveryRate()
 function finalizeDeliveryRate() 
 + Reentrancy protection agains IMech(mech).maxDeliveryRate()
 ```
-[]
+[x] Fixed
 
 #### Notices. unintuitive name vs action
 ```
 function _checkNativeValue() internal virtual override
 The function name is very unintuitive. In reality, it just does a revert if the contract type is token.
 ```
-[]
+[x] Fixed
 
 #### Notices. checkAndRecordDeliveryRate why are uint256 parameters needed
 ```
@@ -53,4 +54,4 @@ Why unused params?
         uint256
 If this is abstract data for the future, it is better to replace it with bytes payload.
 ```
-[]
\ No newline at end of file
+[x] Fixed
\ No newline at end of file
diff --git a/contracts/BalanceTrackerFixedPriceBase.sol b/contracts/BalanceTrackerFixedPriceBase.sol
index fec502e..d177c84 100644
--- a/contracts/BalanceTrackerFixedPriceBase.sol
+++ b/contracts/BalanceTrackerFixedPriceBase.sol
@@ -82,7 +82,7 @@ abstract contract BalanceTrackerFixedPriceBase {
         buyBackBurner = _buyBackBurner;
     }
 
-    function _checkNativeValue() internal virtual;
+    function _getOrRestrictNativeValue() internal virtual returns (uint256);
 
     function _getRequiredFunds(address requester, uint256 balanceDiff) internal virtual returns (uint256);
 
@@ -92,26 +92,26 @@ abstract contract BalanceTrackerFixedPriceBase {
         address requester,
         bytes memory
     ) external payable {
+        // Reentrancy guard
+        if (_locked > 1) {
+            revert ReentrancyGuard();
+        }
+        _locked = 2;
+
         // Check for marketplace access
         if (msg.sender != mechMarketplace) {
             revert MarketplaceOnly(msg.sender, mechMarketplace);
         }
 
         // Check for native value
-        _checkNativeValue();
+        uint256 initAmount = _getOrRestrictNativeValue();
+
+        // Get account balance
+        uint256 balance = mapRequesterBalances[requester] + initAmount;
 
         // Get mech max delivery rate
         uint256 maxDeliveryRate = IMech(mech).maxDeliveryRate();
 
-        // Get account balance
-        uint256 balance = mapRequesterBalances[requester];
-
-        // Update balance with native value
-        if (msg.value > 0) {
-            balance += msg.value;
-            emit Deposit(msg.sender, address(0), msg.value);
-        }
-        
         // Check the request delivery rate for a fixed price
         if (balance < maxDeliveryRate) {
             // Get balance difference
@@ -127,6 +127,8 @@ abstract contract BalanceTrackerFixedPriceBase {
         // Adjust account balance
         balance -= maxDeliveryRate;
         mapRequesterBalances[requester] = balance;
+
+        _locked = 1;
     }
 
     /// @dev Finalizes mech delivery rate based on requested and actual ones.
diff --git a/contracts/BalanceTrackerFixedPriceNative.sol b/contracts/BalanceTrackerFixedPriceNative.sol
index d383196..067f1ee 100644
--- a/contracts/BalanceTrackerFixedPriceNative.sol
+++ b/contracts/BalanceTrackerFixedPriceNative.sol
@@ -35,7 +35,14 @@ contract BalanceTrackerFixedPriceNative is BalanceTrackerFixedPriceBase {
         wrappedNativeToken = _wrappedNativeToken;
     }
 
-    function _checkNativeValue() internal virtual override {}
+    function _getOrRestrictNativeValue() internal virtual override returns (uint256) {
+        // Update balance with native value
+        if (msg.value > 0) {
+            emit Deposit(msg.sender, address(0), msg.value);
+        }
+
+        return msg.value;
+    }
 
     function _getRequiredFunds(address, uint256) internal virtual override returns (uint256) {
         return 0;
diff --git a/contracts/BalanceTrackerFixedPriceToken.sol b/contracts/BalanceTrackerFixedPriceToken.sol
index 048ddf8..e446525 100644
--- a/contracts/BalanceTrackerFixedPriceToken.sol
+++ b/contracts/BalanceTrackerFixedPriceToken.sol
@@ -17,6 +17,11 @@ interface IToken {
     /// @param amount Amount to transfer to.
     /// @return True if the function execution is successful.
     function transferFrom(address from, address to, uint256 amount) external returns (bool);
+
+    /// @dev Gets the amount of tokens owned by a specified account.
+    /// @param account Account address.
+    /// @return Amount of tokens owned.
+    function balanceOf(address account) external view returns (uint256);
 }
 
 contract BalanceTrackerFixedPriceNative is BalanceTrackerFixedPriceBase {
@@ -38,16 +43,29 @@ contract BalanceTrackerFixedPriceNative is BalanceTrackerFixedPriceBase {
         olas = _olas;
     }
 
-    function _checkNativeValue() internal virtual override {
+    function _getOrRestrictNativeValue() internal virtual override returns (uint256) {
         // Check for msg.value
         if (msg.value > 0) {
             revert NoDepositAllowed(msg.value);
         }
+
+        return 0;
     }
 
     function _getRequiredFunds(address requester, uint256 balanceDiff) internal virtual override returns (uint256) {
-        // TODO check balances before and after
+        uint256 balanceBefore = IToken(olas).balanceOf(address(this));
+        // Get tokens from requester
         IToken(olas).transferFrom(requester, address(this), balanceDiff);
+        uint256 balanceAfter = IToken(olas).balanceOf(address(this));
+
+        // Check the balance
+        uint256 diff = balanceAfter - balanceBefore;
+        if (diff != balanceDiff) {
+            revert TransferFailed(olas, requester, address(this), balanceDiff);
+        }
+
+        emit Deposit(msg.sender, olas, balanceDiff);
+
         return balanceDiff;
     }
 
diff --git a/contracts/MechFactoryFixedPriceNative.sol b/contracts/MechFactoryFixedPriceNative.sol
index e9c8eae..33653f9 100644
--- a/contracts/MechFactoryFixedPriceNative.sol
+++ b/contracts/MechFactoryFixedPriceNative.sol
@@ -8,12 +8,22 @@ import {MechFixedPriceNative} from "./MechFixedPriceNative.sol";
 /// @param expected Expected data length.
 error IncorrectDataLength(uint256 provided, uint256 expected);
 
+/// @dev Only `marketplace` has a privilege, but the `sender` was provided.
+/// @param sender Sender address.
+/// @param marketplace Required marketplace address.
+error MarketplaceOnly(address sender, address marketplace);
+
+/// @dev Provided zero address.
+error ZeroAddress();
+
 /// @title Mech Factory Basic - Periphery smart contract for managing basic mech creation
 contract MechFactoryFixedPriceNative {
     event CreateFixedPriceMech(address indexed mech, uint256 indexed serviceId, uint256 maxDeliveryRate);
 
     // Agent factory version number
     string public constant VERSION = "0.1.0";
+    // Nonce
+    uint256 internal _nonce;
 
     /// @dev Registers service as a mech.
     /// @param mechMarketplace Mech marketplace address.
@@ -27,7 +37,10 @@ contract MechFactoryFixedPriceNative {
         uint256 serviceId,
         bytes memory payload
     ) external returns (address mech) {
-        // TODO: restrict all factories to be called from marketplace only - makes it easier to monitor the system
+        // Check for marketplace access
+        if (msg.sender != mechMarketplace) {
+            revert MarketplaceOnly(msg.sender, mechMarketplace);
+        }
 
         // Check payload length
         if (payload.length != 32) {
@@ -37,12 +50,19 @@ contract MechFactoryFixedPriceNative {
         // Decode max delivery rate
         uint256 maxDeliveryRate = abi.decode(payload, (uint256));
 
+        uint256 localNonce = _nonce;
         // Get salt
-        bytes32 salt = keccak256(abi.encode(block.timestamp, msg.sender, serviceId));
+        bytes32 salt = keccak256(abi.encode(block.timestamp, msg.sender, serviceId, localNonce));
+        _nonce = localNonce + 1;
 
         // Service multisig is isOperator() for the mech
         mech = address((new MechFixedPriceNative){salt: salt}(mechMarketplace, serviceRegistry, serviceId, maxDeliveryRate));
 
+        // Check for zero address
+        if (mech == address(0)) {
+            revert ZeroAddress();
+        }
+
         emit CreateFixedPriceMech(mech, serviceId, maxDeliveryRate);
     }
 }
diff --git a/contracts/MechFactoryFixedPriceToken.sol b/contracts/MechFactoryFixedPriceToken.sol
index 5039915..3436b8e 100644
--- a/contracts/MechFactoryFixedPriceToken.sol
+++ b/contracts/MechFactoryFixedPriceToken.sol
@@ -8,12 +8,22 @@ import {MechFixedPriceToken} from "./MechFixedPriceToken.sol";
 /// @param expected Expected data length.
 error IncorrectDataLength(uint256 provided, uint256 expected);
 
+/// @dev Only `marketplace` has a privilege, but the `sender` was provided.
+/// @param sender Sender address.
+/// @param marketplace Required marketplace address.
+error MarketplaceOnly(address sender, address marketplace);
+
+/// @dev Provided zero address.
+error ZeroAddress();
+
 /// @title Mech Factory Basic - Periphery smart contract for managing basic mech creation
 contract MechFactoryFixedPriceNative {
     event CreateFixedPriceMech(address indexed mech, uint256 indexed serviceId, uint256 maxDeliveryRate);
 
     // Agent factory version number
     string public constant VERSION = "0.1.0";
+    // Nonce
+    uint256 internal _nonce;
 
     /// @dev Registers service as a mech.
     /// @param mechMarketplace Mech marketplace address.
@@ -27,6 +37,11 @@ contract MechFactoryFixedPriceNative {
         uint256 serviceId,
         bytes memory payload
     ) external returns (address mech) {
+        // Check for marketplace access
+        if (msg.sender != mechMarketplace) {
+            revert MarketplaceOnly(msg.sender, mechMarketplace);
+        }
+
         // Check payload length
         if (payload.length != 32) {
             revert IncorrectDataLength(payload.length, 32);
@@ -35,12 +50,19 @@ contract MechFactoryFixedPriceNative {
         // Decode max delivery rate
         uint256 maxDeliveryRate = abi.decode(payload, (uint256));
 
+        uint256 localNonce = _nonce;
         // Get salt
-        bytes32 salt = keccak256(abi.encode(block.timestamp, msg.sender, serviceId));
+        bytes32 salt = keccak256(abi.encode(block.timestamp, msg.sender, serviceId, localNonce));
+        _nonce = localNonce + 1;
 
         // Service multisig is isOperator() for the mech
         mech = address((new MechFixedPriceToken){salt: salt}(mechMarketplace, serviceRegistry, serviceId, maxDeliveryRate));
 
+        // Check for zero address
+        if (mech == address(0)) {
+            revert ZeroAddress();
+        }
+
         emit CreateFixedPriceMech(mech, serviceId, maxDeliveryRate);
     }
 }
diff --git a/contracts/MechFixedPriceNative.sol b/contracts/MechFixedPriceNative.sol
index d4fb65b..963f074 100644
--- a/contracts/MechFixedPriceNative.sol
+++ b/contracts/MechFixedPriceNative.sol
@@ -5,13 +5,16 @@ import {OlasMech} from "./OlasMech.sol";
 
 /// @title MechFixedPriceNative - Smart contract for OlasMech that accepts a fixed price payment for services in native token.
 contract MechFixedPriceNative is OlasMech {
+    // keccak256(FixedPriceNative) = ba699a34be8fe0e7725e93dcbce1701b0211a8ca61330aaeb8a05bf2ec7abed1
+    bytes32 public constant PAYMENT_TYPE = 0xba699a34be8fe0e7725e93dcbce1701b0211a8ca61330aaeb8a05bf2ec7abed1;
+
     /// @dev AgentMech constructor.
     /// @param _mechMarketplace Mech marketplace address.
     /// @param _serviceRegistry Address of the token contract.
     /// @param _serviceId Service Id.
     /// @param _maxDeliveryRate The maximum delivery rate.
     constructor(address _mechMarketplace, address _serviceRegistry, uint256 _serviceId, uint256 _maxDeliveryRate)
-        OlasMech(_mechMarketplace, _serviceRegistry, _serviceId, _maxDeliveryRate, PaymentType.FixedPriceNative)
+        OlasMech(_mechMarketplace, _serviceRegistry, _serviceId, _maxDeliveryRate, PAYMENT_TYPE)
     {}
 
     /// @dev Performs actions before the delivery of a request.
diff --git a/contracts/MechFixedPriceToken.sol b/contracts/MechFixedPriceToken.sol
index 3b44018..6144d21 100644
--- a/contracts/MechFixedPriceToken.sol
+++ b/contracts/MechFixedPriceToken.sol
@@ -5,13 +5,16 @@ import {OlasMech} from "./OlasMech.sol";
 
 /// @title MechFixedPriceToken - Smart contract for OlasMech that accepts a fixed price payment for services in native token.
 contract MechFixedPriceToken is OlasMech {
+    // keccak256(FixedPriceToken) = 3679d66ef546e66ce9057c4a052f317b135bc8e8c509638f7966edfd4fcf45e9
+    bytes32 public constant PAYMENT_TYPE = 0x3679d66ef546e66ce9057c4a052f317b135bc8e8c509638f7966edfd4fcf45e9;
+
     /// @dev AgentMech constructor.
     /// @param _mechMarketplace Mech marketplace address.
     /// @param _serviceRegistry Address of the token contract.
     /// @param _serviceId Service Id.
     /// @param _maxDeliveryRate The maximum delivery rate.
     constructor(address _mechMarketplace, address _serviceRegistry, uint256 _serviceId, uint256 _maxDeliveryRate)
-        OlasMech(_mechMarketplace, _serviceRegistry, _serviceId, _maxDeliveryRate, PaymentType.FixedPriceToken)
+        OlasMech(_mechMarketplace, _serviceRegistry, _serviceId, _maxDeliveryRate, PAYMENT_TYPE)
     {}
 
     /// @dev Performs actions before the delivery of a request.
diff --git a/contracts/MechMarketplace.sol b/contracts/MechMarketplace.sol
index 9c40194..5afea9e 100644
--- a/contracts/MechMarketplace.sol
+++ b/contracts/MechMarketplace.sol
@@ -32,7 +32,7 @@ struct MechDelivery {
     uint256 deliveryRate;
 }
 
-/// @title Mech Marketplace - Marketplace for posting and delivering requests served by agent mechs
+/// @title Mech Marketplace - Marketplace for posting and delivering requests served by mechs
 /// @author Aleksandr Kuperman - <aleksandr.kuperman@valory.xyz>
 /// @author Andrey Lebedev - <andrey.lebedev@valory.xyz>
 /// @author Silvere Gangloff - <silvere.gangloff@valory.xyz>
@@ -42,7 +42,7 @@ contract MechMarketplace is IErrorsMarketplace {
     event ImplementationUpdated(address indexed implementation);
     event MarketplaceParamsUpdated(uint256 fee, uint256 minResponseTimeout, uint256 maxResponseTimeout);
     event SetMechFactoryStatuses(address[] mechFactories, bool[] statuses);
-    event SetPaymentTypeBalanceTrackers(uint8[] paymentTypes, address[] balanceTrackers);
+    event SetPaymentTypeBalanceTrackers(bytes32[] paymentTypes, address[] balanceTrackers);
     event MarketplaceRequest(address indexed requester, address indexed requestedMech, uint256 requestId, bytes data);
     event MarketplaceDeliver(address indexed priorityMech, address indexed actualMech, address indexed requester,
         uint256 requestId, bytes data);
@@ -89,13 +89,12 @@ contract MechMarketplace is IErrorsMarketplace {
     // Contract owner
     address public owner;
 
-    // TODO: Aren't we duplicating info hereand on mech re the address specific counts?
     // Map of request counts for corresponding requester
     mapping(address => uint256) public mapRequestCounts;
     // Map of delivery counts for corresponding requester
     mapping(address => uint256) public mapDeliveryCounts;
     // Map of delivery counts for mechs
-    mapping(address => uint256) public mapAgentMechDeliveryCounts;
+    mapping(address => uint256) public mapMechDeliveryCounts;
     // Map of delivery counts for corresponding mech service multisig
     mapping(address => uint256) public mapMechServiceDeliveryCounts;
     // Mapping of request Id => mech delivery information
@@ -104,8 +103,8 @@ contract MechMarketplace is IErrorsMarketplace {
     mapping(address => bool) public mapMechFactories;
     // Map of mech => its creating factory
     mapping(address => address) public mapAgentMechFactories;
-    // Map of mech type => balanceTracker address
-    mapping(uint8 => address) public mapPaymentTypeBalanceTrackers;
+    // Map of payment type => balanceTracker address
+    mapping(bytes32 => address) public mapPaymentTypeBalanceTrackers;
     // Mapping of account nonces
     mapping(address => uint256) public mapNonces;
     // Mapping of service ids to mechs
@@ -307,7 +306,7 @@ contract MechMarketplace is IErrorsMarketplace {
     /// @dev Sets mech payment type balanceTrackers.
     /// @param paymentTypes Mech types.
     /// @param balanceTrackers Corresponding balanceTracker addresses.
-    function setPaymentTypeBalanceTrackers(uint8[] memory paymentTypes, address[] memory balanceTrackers) external {
+    function setPaymentTypeBalanceTrackers(bytes32[] memory paymentTypes, address[] memory balanceTrackers) external {
         // Check for the ownership
         if (msg.sender != owner) {
             revert OwnerOnly(msg.sender, owner);
@@ -378,7 +377,7 @@ contract MechMarketplace is IErrorsMarketplace {
         requestId = getRequestId(msg.sender, data, mapNonces[msg.sender]);
 
         // Get balance tracker address
-        uint8 mechPaymentType = IMech(priorityMech).getPaymentType();
+        bytes32 mechPaymentType = IMech(priorityMech).paymentType();
         address balanceTracker = mapPaymentTypeBalanceTrackers[mechPaymentType];
 
         // Check and record mech delivery rate
@@ -423,7 +422,7 @@ contract MechMarketplace is IErrorsMarketplace {
     /// @param requestData Self-descriptive opaque data-blob.
     function deliverMarketplace(
         uint256 requestId,
-        bytes memory requestData,
+        bytes memory requestData
     ) external {
         // Reentrancy guard
         if (_locked > 1) {
@@ -468,9 +467,9 @@ contract MechMarketplace is IErrorsMarketplace {
         // Decrease the number of undelivered requests
         numUndeliveredRequests--;
         // Increase the amount of requester delivered requests
-        mapDeliveryCounts[requester]++;
+        mapDeliveryCounts[mechDelivery.requester]++;
         // Increase the amount of mech delivery counts
-        mapAgentMechDeliveryCounts[msg.sender]++;
+        mapMechDeliveryCounts[msg.sender]++;
         // Increase the amount of mech service multisig delivered requests
         mapMechServiceDeliveryCounts[mechServiceMultisig]++;
 
@@ -478,14 +477,14 @@ contract MechMarketplace is IErrorsMarketplace {
         IKarma(karma).changeMechKarma(msg.sender, 1);
 
         // Get balance tracker address
-        uint8 mechPaymentType = IMech(priorityMech).getPaymentType();
+        bytes32 mechPaymentType = IMech(priorityMech).paymentType();
         address balanceTracker = mapPaymentTypeBalanceTrackers[mechPaymentType];
 
         // Process payment
         IBalanceTracker(balanceTracker).finalizeDeliveryRate(msg.sender, mechDelivery.requester, requestId,
             mechDelivery.deliveryRate);
 
-        emit MarketplaceDeliver(priorityMech, msg.sender, requester, requestId, requestData);
+        emit MarketplaceDeliver(priorityMech, msg.sender, mechDelivery.requester, requestId, requestData);
 
         _locked = 1;
     }
@@ -537,17 +536,9 @@ contract MechMarketplace is IErrorsMarketplace {
     }
 
     /// @dev Checks for mech validity.
-    /// @dev mech Agent mech contract address.
-    /// @param mechServiceId Agent mech service Id.
-    /// @return multisig
-    function checkMech(
-        address mech,
-    ) public view returns (address multisig) {
-        // Check for zero value
-        if (mechServiceId == 0) {
-            revert ZeroValue();
-        }
-
+    /// @param mech Mech contract address.
+    /// @return multisig Mech service multisig address.
+    function checkMech(address mech) public view returns (address multisig){
         uint256 mechServiceId = IMech(mech).tokenId();
 
         // Check mech validity as it must be created and recorded via this marketplace
@@ -555,7 +546,7 @@ contract MechMarketplace is IErrorsMarketplace {
             revert UnauthorizedAccount(mech);
         }
 
-        // Check mech service Id, if applicable
+        // Check mech service Id
         multisig = checkServiceAndGetMultisig(mechServiceId);
 
         // Check that service multisig is the priority mech service multisig
@@ -566,7 +557,7 @@ contract MechMarketplace is IErrorsMarketplace {
 
     /// @dev Checks for requester validity.
     /// @notice Explicitly allows for EOAs without service id.
-    /// @dev requester Requester contract address.
+    /// @param requester Requester address.
     /// @param requesterServiceId Requester service Id.
     function checkRequester(
         address requester,
@@ -602,41 +593,5 @@ contract MechMarketplace is IErrorsMarketplace {
             }
         }
     }
-
-    /// @dev Gets the requests count for a specific account.
-    /// @param account Account address.
-    /// @return Requests count.
-    function getRequestsCount(address account) external view returns (uint256) {
-        return mapRequestCounts[account];
-    }
-
-    /// @dev Gets the deliveries count for a specific account.
-    /// @param account Account address.
-    /// @return Deliveries count.
-    function getDeliveriesCount(address account) external view returns (uint256) {
-        return mapDeliveryCounts[account];
-    }
-
-    // TODO Check if needed
-    /// @dev Gets deliveries count for a specific mech.
-    /// @param agentMech Agent mech address.
-    /// @return Deliveries count.
-    function getAgentMechDeliveriesCount(address agentMech) external view returns (uint256) {
-        return mapAgentMechDeliveryCounts[agentMech];
-    }
-
-    /// @dev Gets deliveries count for a specific mech service multisig.
-    /// @param mechServiceMultisig Agent mech service multisig address.
-    /// @return Deliveries count.
-    function getMechServiceDeliveriesCount(address mechServiceMultisig) external view returns (uint256) {
-        return mapMechServiceDeliveryCounts[mechServiceMultisig];
-    }
-
-    /// @dev Gets mech delivery info.
-    /// @param requestId Request Id.
-    /// @return Mech delivery info.
-    function getMechDeliveryInfo(uint256 requestId) external view returns (MechDelivery memory) {
-        return mapRequestIdDeliveries[requestId];
-    }
 }
 
diff --git a/contracts/OlasMech.sol b/contracts/OlasMech.sol
index 12c30df..f36b498 100644
--- a/contracts/OlasMech.sol
+++ b/contracts/OlasMech.sol
@@ -14,12 +14,6 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
     event Request(address indexed sender, uint256 requestId, bytes data);
     event RevokeRequest(address indexed sender, uint256 requestId);
 
-    enum PaymentType { // this level of the contract should not have to specify its possible extensions. So Payment type needs to be something that's extensible, string or number..
-        FixedPriceNative,
-        FixedPriceToken,
-        NvmSubscription
-    }
-
     enum RequestStatus {
         DoesNotExist,
         Requested,
@@ -38,8 +32,7 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
     // Mech marketplace address
     address public immutable mechMarketplace;
     // Mech payment type
-    // TODO - can it be id or string so its' forward compatible?
-    PaymentType public immutable paymentType;
+    bytes32 public immutable paymentType;
 
     // TODO give it a better name
     // Maximum required delivery rate
@@ -53,20 +46,12 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
     // Reentrancy lock
     uint256 internal _locked = 1;
 
-    // TODO do we need the next two maps? Is it for staking activity checks?
-    // Map of request counts for corresponding addresses in this agent mech
-    mapping(address => uint256) public mapRequestCounts;
-    // Map of delivery counts for corresponding addresses in this agent mech
-    mapping(address => uint256) public mapDeliveryCounts;
     // Map of undelivered requests counts for corresponding addresses in this agent mech
     mapping(address => uint256) public mapUndeliveredRequestsCounts;
     // Cyclical map of request Ids
     mapping(uint256 => uint256[2]) public mapRequestIds;
     // Map of request Id => sender address
     mapping(uint256 => address) public mapRequestAddresses;
-    // TODO is a global nonce not sufficient?
-    // Mapping of account nonces
-    mapping(address => uint256) public mapNonces;
 
     /// @param _mechMarketplace Mech marketplace address.
     /// @param _serviceRegistry Address of the registry contract.
@@ -75,8 +60,8 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
         address _mechMarketplace,
         address _serviceRegistry,
         uint256 _serviceId,
-        uint256 _maxDeliveryRate, // TODO - for subscriptions, why do we even specify this here; it should be specified by the requester
-        PaymentType _paymentType
+        uint256 _maxDeliveryRate,
+        bytes32 _paymentType
     ) {
         // Check for zero address
         if (mechMarketplace == address(0)) {
@@ -89,7 +74,7 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
         }
 
         // Check for zero value
-        if (_serviceId == 0 || _maxDeliveryRate == 0) {
+        if (_serviceId == 0 || _maxDeliveryRate == 0 || _paymentType == 0) {
             revert ZeroValue();
         }
 
@@ -112,7 +97,6 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
         maxDeliveryRate = _maxDeliveryRate;
         paymentType = _paymentType;
 
-
         // Record chain Id
         chainId = block.chainid;
         // Compute domain separator
@@ -133,9 +117,9 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
         );
     }
 
-    // TODO TBD
+    // TODO Rename account for requester
     /// @dev Performs actions before the delivery of a request.
-    /// @param account Request sender address.
+    /// @param account Requester address.
     /// @param requestId Request Id.
     /// @param data Self-descriptive opaque data-blob.
     /// @return requestData Data for the request processing.
@@ -146,7 +130,7 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
     ) internal virtual returns (bytes memory requestData);
 
     /// @dev Registers a request.
-    /// @param account Requester account address.
+    /// @param account Requester address.
     /// @param requestId Request Id.
     /// @param data Self-descriptive opaque data-blob.
     function _request(
@@ -154,8 +138,6 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
         uint256 requestId,
         bytes memory data
     ) internal virtual {
-        // Increase the requests count supplied by the sender
-        mapRequestCounts[account]++;
         mapUndeliveredRequestsCounts[account]++;
         // Record the requestId => sender correspondence
         mapRequestAddresses[requestId] = account;
@@ -223,7 +205,7 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
         }
 
         // Check for max delivery rate compared to requested one
-        if (maxDeliveryRate < mechDelivery.deliveryRate) {
+        if (maxDeliveryRate > mechDelivery.deliveryRate) {
             revert Overflow(maxDeliveryRate, mechDelivery.deliveryRate);
         }
 
@@ -244,7 +226,6 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
         requestData = _preDeliver(account, requestId, data);
 
         // Increase the total number of deliveries, as the request is delivered by this mech
-        mapDeliveryCounts[account]++;
         numTotalDeliveries++;
 
         emit Deliver(msg.sender, requestId, requestData);
@@ -304,7 +285,7 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
     /// @param data Self-descriptive opaque data-blob.
     function deliverToMarketplace(
         uint256 requestId,
-        bytes memory data,
+        bytes memory data
     ) external onlyOperator {
         // Reentrancy guard
         if (_locked > 1) {
@@ -317,8 +298,7 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
 
         // Mech marketplace delivery finalization if the request was not delivered already
         if (requestData.length > 0) {
-            IMechMarketplace(mechMarketplace).deliverMarketplace(requestId, requestData,
-                tokenId());
+            IMechMarketplace(mechMarketplace).deliverMarketplace(requestId, requestData, tokenId());
         }
 
         _locked = 1;
@@ -345,11 +325,11 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
         );
 
         (, address multisig, , , , , IServiceRegistry.ServiceState state) =
-            IServiceRegistry(_serviceRegistry).mapServices(tokenId());
+            IServiceRegistry(serviceRegistry).mapServices(serviceId);
 
         // Check for correct service state
         if (state != IServiceRegistry.ServiceState.Deployed) {
-            revert WrongServiceState(uint256(state), tokenId());
+            revert WrongServiceState(uint256(state), serviceId);
         }
         return multisig == signer;
     }
@@ -385,20 +365,6 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
         ));
     }
 
-    /// @dev Gets the requests count for a specific account.
-    /// @param account Account address.
-    /// @return Requests count.
-    function getRequestsCount(address account) external view returns (uint256) {
-        return mapRequestCounts[account];
-    }
-
-    /// @dev Gets the deliveries count for a specific account.
-    /// @param account Account address.
-    /// @return Deliveries count.
-    function getDeliveriesCount(address account) external view returns (uint256) {
-        return mapDeliveryCounts[account];
-    }
-
     /// @dev Gets the request Id status registered in this agent mech.
     /// @notice If marketplace is not zero, use the same function in the mech marketplace contract.
     /// @param requestId Request Id.
@@ -456,11 +422,6 @@ abstract contract OlasMech is Mech, IErrorsMech, ImmutableStorage {
         }
     }
 
-
-    function getPaymentType() external view returns (uint8) {
-        return uint8(paymentType);
-    }
-
     /// @dev Gets finalized delivery rate for a request Id.
     /// @param requestId Request Id.
     /// @return Finalized delivery rate.
diff --git a/contracts/integrations/nevermined/MechFactoryNvmSubscription.sol b/contracts/integrations/nevermined/MechFactoryNvmSubscription.sol
index 2b5d63a..076c14c 100644
--- a/contracts/integrations/nevermined/MechFactoryNvmSubscription.sol
+++ b/contracts/integrations/nevermined/MechFactoryNvmSubscription.sol
@@ -8,12 +8,22 @@ import {MechNvmSubscription} from "./MechNvmSubscription.sol";
 /// @param expected Expected data length.
 error IncorrectDataLength(uint256 provided, uint256 expected);
 
+/// @dev Only `marketplace` has a privilege, but the `sender` was provided.
+/// @param sender Sender address.
+/// @param marketplace Required marketplace address.
+error MarketplaceOnly(address sender, address marketplace);
+
+/// @dev Provided zero address.
+error ZeroAddress();
+
 /// @title MechFactoryNvmSubscription - Periphery smart contract for managing Nevermined subscription mech creation
 contract MechFactoryNvmSubscription {
     event CreateSubscriptionMech(address indexed mech, uint256 indexed serviceId, uint256 maxDeliveryRate);
 
     // Agent factory version number
     string public constant VERSION = "0.1.0";
+    // Nonce
+    uint256 internal _nonce;
 
     /// @dev Registers service as a mech.
     /// @param mechMarketplace Mech marketplace address.
@@ -27,6 +37,11 @@ contract MechFactoryNvmSubscription {
         uint256 serviceId,
         bytes memory payload
     ) external returns (address mech) {
+        // Check for marketplace access
+        if (msg.sender != mechMarketplace) {
+            revert MarketplaceOnly(msg.sender, mechMarketplace);
+        }
+
         // Check payload length
         if (payload.length != 32) {
             revert IncorrectDataLength(payload.length, 32);
@@ -35,13 +50,20 @@ contract MechFactoryNvmSubscription {
         // Decode subscription parameters
         uint256 maxDeliveryRate = abi.decode(payload, (uint256));
 
+        uint256 localNonce = _nonce;
         // Get salt
-        bytes32 salt = keccak256(abi.encode(block.timestamp, msg.sender, serviceId));
+        bytes32 salt = keccak256(abi.encode(block.timestamp, msg.sender, serviceId, localNonce));
+        _nonce = localNonce + 1;
 
         // Service multisig is isOperator() for the mech
         mech = address((new MechNvmSubscription){salt: salt}(mechMarketplace, serviceRegistry, serviceId,
             maxDeliveryRate));
 
+        // Check for zero address
+        if (mech == address(0)) {
+            revert ZeroAddress();
+        }
+
         emit CreateSubscriptionMech(mech, serviceId, maxDeliveryRate);
     }
 }
diff --git a/contracts/integrations/nevermined/MechNvmSubscription.sol b/contracts/integrations/nevermined/MechNvmSubscription.sol
index 18fc59f..d943e5e 100644
--- a/contracts/integrations/nevermined/MechNvmSubscription.sol
+++ b/contracts/integrations/nevermined/MechNvmSubscription.sol
@@ -28,6 +28,9 @@ error ZeroValue();
 contract MechNvmSubscription is OlasMech {
     event RequestRateFinalized(uint256 indexed requestId, uint256 deliveryRate);
 
+    // keccak256(NvmSubscription) = 626e3e03bc0d3f35fa97066f92f71221d599a2bcf50a2c9d6cfa6572204006a0
+    bytes32 public constant PAYMENT_TYPE = 0x626e3e03bc0d3f35fa97066f92f71221d599a2bcf50a2c9d6cfa6572204006a0;
+
     // Mapping for requestId => finalized delivery rates
     mapping(uint256 => uint256) public mapRequestIdFinalizedRates;
 
@@ -42,7 +45,7 @@ contract MechNvmSubscription is OlasMech {
         uint256 _serviceId,
         uint256 _maxDeliveryRate
     )
-        OlasMech(_mechMarketplace, _serviceRegistry, _serviceId, _maxDeliveryRate, PaymentType.NvmSubscription)
+        OlasMech(_mechMarketplace, _serviceRegistry, _serviceId, _maxDeliveryRate, PAYMENT_TYPE)
     {}
 
     /// @dev Performs actions before the delivery of a request.
diff --git a/contracts/interfaces/IMech.sol b/contracts/interfaces/IMech.sol
index 461f0d5..7ec304a 100644
--- a/contracts/interfaces/IMech.sol
+++ b/contracts/interfaces/IMech.sol
@@ -19,10 +19,12 @@ interface IMech {
 
     function maxDeliveryRate() external returns (uint256);
 
-    function getPaymentType() external returns (uint8);
+    function paymentType() external returns (bytes32);
 
     /// @dev Gets finalized delivery rate for a request Id.
     /// @param requestId Request Id.
     /// @return Finalized delivery rate.
     function getFinalizedDeliveryRate(uint256 requestId) external returns (uint256);
+
+    function tokenId() external view returns (uint256);
 }
\ No newline at end of file
diff --git a/contracts/interfaces/IMechMarketplace.sol b/contracts/interfaces/IMechMarketplace.sol
index 6417713..a027e7b 100644
--- a/contracts/interfaces/IMechMarketplace.sol
+++ b/contracts/interfaces/IMechMarketplace.sol
@@ -20,12 +20,10 @@ interface IMechMarketplace {
     /// @dev Delivers a request.
     /// @param requestId Request id.
     /// @param requestData Self-descriptive opaque data-blob.
-    /// @param deliveryMechStakingInstance Delivery mech staking instance address (optional).
     /// @param deliveryMechServiceId Mech operator service Id.
     function deliverMarketplace(
         uint256 requestId,
         bytes memory requestData,
-        address deliveryMechStakingInstance,
         uint256 deliveryMechServiceId
     ) external;