diff --git a/src/tx-format/index.md b/src/tx-format/index.md
index b53e214d..bfc91a1f 100644
--- a/src/tx-format/index.md
+++ b/src/tx-format/index.md
@@ -18,4 +18,5 @@ The Fuel Transaction Format.
   - [`OutputVariable`](./output.md#outputvariable)
   - [`OutputContractCreated`](./output.md#outputcontractcreated)
 - [`Witness`](./witness.md)
+- [`Policy`](./policy.md)
 - [`TXPointer`](./tx-pointer.md)
diff --git a/src/tx-format/policy.md b/src/tx-format/policy.md
index b03dbaea..c4b95b47 100644
--- a/src/tx-format/policy.md
+++ b/src/tx-format/policy.md
@@ -44,11 +44,12 @@ Transaction is invalid if:
 
 ## `MaxFee`
 
-| name      | type     | description                                                     |
-|-----------|----------|-----------------------------------------------------------------|
-| `max_fee` | `uint64` | The maximum fee payable by this transaction using `BASE_ASSET`. |
+| name      | type     | description                                                                                                                                |
+|-----------|----------|--------------------------------------------------------------------------------------------------------------------------------------------|
+| `max_fee` | `uint64` | The maximum fee payable by this transaction using `BASE_ASSET`. This is used to check transactions before the actual `gas_price` is known. |
 
 Transaction is invalid if:
 
+- `max_fee` is not set
 - `max_fee > sum_inputs(tx, BASE_ASSET_ID) - sum_outputs(tx, BASE_ASSET_ID)`
 - `max_fee < reserved_fee_balance(tx, BASE_ASSET_ID)`