diff --git a/docs/DeveloperGuide.md b/docs/DeveloperGuide.md
index f439f93ff8..3f1368658a 100644
--- a/docs/DeveloperGuide.md
+++ b/docs/DeveloperGuide.md
@@ -1,5 +1,33 @@
 # Developer Guide
 
+## Table of contents
+
+* [Acknowledgements](#acknowledgements)
+* [Design & implementation](#design--implementation)
+  * [Storage Component](#storage-component)
+    * [Design considerations](#design-considerations)
+  * [Visualization Feature](#visualization-feature-)
+    * [Class diagram](#class-diagram)
+    * [Sequence diagram](#sequence-diagram-)
+  * [Add income/expense feature](#add-incomeexpense-feature)
+    * [Step 1](#step-1)
+    * [Step 2](#step-2)
+    * [Step 3](#step-3)
+    * [Step 4](#step-4)
+    * [Diagrams](#diagrams)
+  * [Budget Feature](#budget-feature)
+    * [Set and update budget](#set-and-update-budget)
+    * [Delete budget](#delete-budget)
+    * [Reset budget](#reset-budget)
+    * [View budget](#view-budget)
+  * [Product Scope](#product-scope)
+    * [Target user profile](#target-user-profile)
+    * [Value proposition](#value-proposition)
+  * [User Stories](#user-stories)
+  * [Non-Functional Requirements](#non-functional-requirements)
+  * [Glossary](#glossary)
+  * [Instructions for manual testing](#instructions-for-manual-testing)
+
 ## Acknowledgements
 
 **Xchart (A Simple Charting Library for Java)**
diff --git a/docs/diagrams/Budget.puml b/docs/diagrams/Budget.puml
index 755ff562c0..11ba20e9e8 100644
--- a/docs/diagrams/Budget.puml
+++ b/docs/diagrams/Budget.puml
@@ -2,10 +2,9 @@
 
 participant ":BudgetCommand" as BudgetCommand
 participant "<<class>>\nBudget" as Budget
-participant "<<class>>\nUi" as Ui
+participant ":Ui" as Ui
 
 -> BudgetCommand: execute()
-BudgetCommand -> Ui: getInstance()
 
 alt set
     BudgetCommand -> Budget: setBudget(budget)
diff --git a/docs/diagrams/deleteBudget.puml b/docs/diagrams/deleteBudget.puml
index e689250914..4a8eb03a13 100644
--- a/docs/diagrams/deleteBudget.puml
+++ b/docs/diagrams/deleteBudget.puml
@@ -3,7 +3,7 @@
 mainframe sd DeleteBudget
 participant ":BudgetCommand" as BudgetCommand
 participant "<<class>>\nBudget" as Budget
-participant "<<class>>\nUi" as Ui
+participant ":Ui" as Ui
 
 alt hasBudget
     BudgetCommand -> Budget: deleteBudget()
diff --git a/docs/diagrams/resetBudget.puml b/docs/diagrams/resetBudget.puml
index 8efef02d34..a21b3c7506 100644
--- a/docs/diagrams/resetBudget.puml
+++ b/docs/diagrams/resetBudget.puml
@@ -3,7 +3,7 @@
 mainframe sd ResetBudget
 participant ":BudgetCommand" as BudgetCommand
 participant "<<class>>\nBudget" as Budget
-participant "<<class>>\nUi" as Ui
+participant ":Ui" as Ui
 
 alt spentBudget
     opt initialBudgetExceedBalance
diff --git a/docs/diagrams/viewBudget.puml b/docs/diagrams/viewBudget.puml
index 39c9ec1ccb..02c0d77042 100644
--- a/docs/diagrams/viewBudget.puml
+++ b/docs/diagrams/viewBudget.puml
@@ -3,7 +3,7 @@
 mainframe sd ViewBudget
 participant ":BudgetCommand" as BudgetCommand
 participant "<<class>>\nBudget" as Budget
-participant "<<class>>\nUi" as Ui
+participant ":Ui" as Ui
 
 alt hasBudget
     BudgetCommand -> Ui: printBudget()
diff --git a/docs/images/Budget.png b/docs/images/Budget.png
index 7a140e5cdf..89c18a4ef7 100644
Binary files a/docs/images/Budget.png and b/docs/images/Budget.png differ
diff --git a/docs/images/deleteBudget.png b/docs/images/deleteBudget.png
index 761a4c3620..5857625618 100644
Binary files a/docs/images/deleteBudget.png and b/docs/images/deleteBudget.png differ
diff --git a/docs/images/resetBudget.png b/docs/images/resetBudget.png
index e9f8f5e578..0ea63d522b 100644
Binary files a/docs/images/resetBudget.png and b/docs/images/resetBudget.png differ
diff --git a/docs/images/viewBudget.png b/docs/images/viewBudget.png
index 02ff716a10..fe7179a4ec 100644
Binary files a/docs/images/viewBudget.png and b/docs/images/viewBudget.png differ
diff --git a/src/main/java/seedu/financialplanner/FinancialPlanner.java b/src/main/java/seedu/financialplanner/FinancialPlanner.java
index bdd75a6d00..6d6e3c33a9 100644
--- a/src/main/java/seedu/financialplanner/FinancialPlanner.java
+++ b/src/main/java/seedu/financialplanner/FinancialPlanner.java
@@ -1,5 +1,6 @@
 package seedu.financialplanner;
 
+import seedu.financialplanner.cashflow.CashflowList;
 import seedu.financialplanner.commands.Command;
 import seedu.financialplanner.commands.ExitCommand;
 import seedu.financialplanner.exceptions.FinancialPlannerException;
@@ -10,21 +11,35 @@
 
 import java.time.LocalDate;
 
+/**
+ * Represents the main class for the Financial Planner.
+ * It manages commands and user interactions.
+ */
 public class FinancialPlanner {
     private static final LocalDate date = LocalDate.now();
     private static final String FILE_PATH = "data/data.txt";
     private final Storage storage = Storage.getInstance();
     private final Ui ui = Ui.getInstance();
     private final WatchList watchList = WatchList.getInstance();
+    private final CashflowList cashflowList = CashflowList.getInstance();
     
     private FinancialPlanner() {
     }
 
+    /**
+     * The main starting point of the Financial Planner.
+     *
+     * @param args Unused.
+     */
     public static void main(String[] args) {
         FinancialPlannerLogger.initialise();
         new FinancialPlanner().run();
     }
 
+    /**
+     * Loads storage from save file and starts the Financial Planner.
+     * Saves the storage to save file upon exit.
+     */
     public void run() {
         try {
             storage.load(FILE_PATH, date);
@@ -50,6 +65,9 @@ public void run() {
         ui.exitMessage();
     }
 
+    /**
+     * Saves existing data to the save file.
+     */
     public void save() {
         try {
             storage.save(FILE_PATH);
diff --git a/src/main/java/seedu/financialplanner/FinancialPlannerLogger.java b/src/main/java/seedu/financialplanner/FinancialPlannerLogger.java
index df085a588b..7751a7e0c5 100644
--- a/src/main/java/seedu/financialplanner/FinancialPlannerLogger.java
+++ b/src/main/java/seedu/financialplanner/FinancialPlannerLogger.java
@@ -6,9 +6,15 @@
 import java.util.logging.SimpleFormatter;
 import java.util.logging.LogManager;
 
+/**
+ * Represents the logger for the Financial Planner.
+ */
 public class FinancialPlannerLogger {
     private static Logger logger = Logger.getLogger("Financial Planner Logger");
 
+    /**
+     * Initialises the logger and saves logging info to a file.
+     */
     public static void initialise() {
         try {
             FileHandler fh = new FileHandler("data/logger.log");
diff --git a/src/main/java/seedu/financialplanner/cashflow/Budget.java b/src/main/java/seedu/financialplanner/cashflow/Budget.java
index 6aaae47a11..6d24cc6939 100644
--- a/src/main/java/seedu/financialplanner/cashflow/Budget.java
+++ b/src/main/java/seedu/financialplanner/cashflow/Budget.java
@@ -2,11 +2,19 @@
 
 import java.text.DecimalFormat;
 
+/**
+ * Represents the monthly budget.
+ */
 public abstract class Budget {
     private static final int MONTH = 30;
     private static double initialBudget = 0;
     private static double currentBudget = 0;
 
+    /**
+     * Sets the monthly budget equal to amount.
+     *
+     * @param amount The monthly budget to be set
+     */
     public static void setBudget(double amount) {
         initialBudget = amount;
         currentBudget = amount;
@@ -14,10 +22,21 @@ public static void setBudget(double amount) {
         assert initialBudget != 0 && currentBudget != 0 : "Initial and current budget should not be 0";
     }
 
+    /**
+     * Returns the initial budget set.
+     *
+     * @return The initial budget.
+     */
     public static double getInitialBudget() {
         return initialBudget;
     }
 
+    /**
+     * Updates initial budget to the new budget and updates the current budget
+     * with the difference between the old initial budget and new initial budget.
+     *
+     * @param budget The budget to be updated to.
+     */
     public static void updateBudget(double budget) {
         double diff;
         if (budget > initialBudget) {
@@ -32,50 +51,104 @@ public static void updateBudget(double budget) {
         assert initialBudget == budget : "Initial budget should be equal to updated budget";
     }
 
+    /**
+     * Returns the current budget.
+     *
+     * @return The current budget.
+     */
     public static double getCurrentBudget() {
         return currentBudget;
     }
 
+    /**
+     * Returns the current budget in 2 decimal places after converting
+     * it into a string.
+     *
+     * @return The current budget in string format.
+     */
     public static String getCurrentBudgetString() {
         DecimalFormat decimalFormat = new DecimalFormat("####0.00");
         return decimalFormat.format(Cashflow.round(currentBudget, 2));
     }
 
+    /**
+     * Returns the initial budget in 2 decimal places after converting
+     * it into a string.
+     *
+     * @return The initial budget in string format.
+     */
     public static String getInitialBudgetString() {
         DecimalFormat decimalFormat = new DecimalFormat("####0.00");
         return decimalFormat.format(Cashflow.round(initialBudget, 2));
     }
 
+    /**
+     * Deducts the current budget by the amount given.
+     *
+     * @param amount The amount to be deducted.
+     */
     public static void deduct(double amount) {
-        Budget.currentBudget -= amount;
+        currentBudget -= amount;
     }
 
+    /**
+     * Loads the budget from the save file.
+     *
+     * @param initial The saved initial budget.
+     * @param current The saved current budget.
+     */
     public static void load(double initial, double current) {
         initialBudget = initial;
         currentBudget = current;
     }
 
+    /**
+     * Checks if there is a budget.
+     *
+     * @return True if there is a budget set, false otherwise.
+     */
     public static boolean hasBudget() {
         return initialBudget != 0;
     }
 
+    /**
+     * Returns a string representation of the budget to be saved to the save file.
+     *
+     * @return A string representation of the budget.
+     */
     public static String formatString() {
         return "B | " + initialBudget + " | " + currentBudget;
     }
 
+    /**
+     * Deletes an existing budget.
+     */
     public static void deleteBudget() {
         initialBudget = 0;
         currentBudget = 0;
     }
 
+    /**
+     * Resets the current budget to initial budget.
+     */
     public static void resetBudget() {
         currentBudget = initialBudget;
     }
 
+    /**
+     * Sets initial budget to the amount given.
+     *
+     * @param amount The amount to be set.
+     */
     public static void setInitialBudget(double amount) {
         initialBudget = amount;
     }
 
+    /**
+     * Updates current budget by adding amount to current budget.
+     *
+     * @param amount The amount to be updated.
+     */
     public static void updateCurrentBudget(double amount) {
         currentBudget += amount;
     }
diff --git a/src/main/java/seedu/financialplanner/commands/BalanceCommand.java b/src/main/java/seedu/financialplanner/commands/BalanceCommand.java
index 152b4da378..540f9df0bf 100644
--- a/src/main/java/seedu/financialplanner/commands/BalanceCommand.java
+++ b/src/main/java/seedu/financialplanner/commands/BalanceCommand.java
@@ -6,9 +6,12 @@
 import java.text.DecimalFormat;
 import java.util.ArrayList;
 
+/**
+ * Represents a command for displaying balance.
+ */
 public class BalanceCommand extends Command {
     private final Ui ui = Ui.getInstance();
-
+    
     public BalanceCommand(RawCommand rawCommand) {
         if (!rawCommand.extraArgs.isEmpty()) {
             String unknownExtraArgument = new ArrayList<>(rawCommand.extraArgs.keySet()).get(0);
@@ -16,8 +19,11 @@ public BalanceCommand(RawCommand rawCommand) {
         }
     }
 
+    /**
+     * Executes the command to display balance.
+     */
     @Override
-    public void execute() throws Exception {
+    public void execute() {
         ui.showMessage("Balance: " + getBalanceString());
     }
 
diff --git a/src/main/java/seedu/financialplanner/commands/BudgetCommand.java b/src/main/java/seedu/financialplanner/commands/BudgetCommand.java
index 9dc8d19547..60f24a66f6 100644
--- a/src/main/java/seedu/financialplanner/commands/BudgetCommand.java
+++ b/src/main/java/seedu/financialplanner/commands/BudgetCommand.java
@@ -9,12 +9,21 @@
 import java.util.logging.Logger;
 import java.util.ArrayList;
 
+/**
+ * Represents a command to manage the budget.
+ */
 public class BudgetCommand extends Command {
     private static final Logger logger = Logger.getLogger("Financial Planner Logger");
     private final Ui ui = Ui.getInstance();
     private double budget;
     private String command;
 
+    /**
+     * Constructs a new BudgetCommand and checks if the user input is a valid command.
+     *
+     * @param rawCommand The raw command containing the arguments and parameters given by the user.
+     * @throws FinancialPlannerException If there is an issue with the command provided.
+     */
     public BudgetCommand(RawCommand rawCommand) throws FinancialPlannerException {
         command = rawCommand.args.get(0);
         if (command.equals("delete") || command.equals("reset") || command.equals("view")) {
@@ -33,6 +42,12 @@ public BudgetCommand(RawCommand rawCommand) throws FinancialPlannerException {
         }
     }
 
+    /**
+     * Checks if budget is a positive number and is lower than or equal to total balance.
+     *
+     * @param rawCommand The raw command containing arguments and parameters given by the user.
+     * @throws FinancialPlannerException If there is an issue with budget format.
+     */
     private void validateBudget(RawCommand rawCommand) throws FinancialPlannerException {
         try {
             logger.log(Level.INFO, "Parsing budget as double");
@@ -48,10 +63,16 @@ private void validateBudget(RawCommand rawCommand) throws FinancialPlannerExcept
 
         if (budget > Cashflow.getBalance()) {
             logger.log(Level.WARNING, "Invalid value for budget");
-            throw new FinancialPlannerException("Budget should be lower than total balance.");
+            throw new FinancialPlannerException("Budget should be lower than or equal to total balance.");
         }
     }
 
+    /**
+     * Checks that the command is valid and in the right format.
+     *
+     * @param rawCommand The raw command containing arguments and parameters given by the user.
+     * @throws FinancialPlannerException If there is an issue with the command or format.
+     */
     private void validateCommandFormat(RawCommand rawCommand) throws FinancialPlannerException {
         if (!command.equals("set") && !command.equals("update")) {
             logger.log(Level.WARNING, "Invalid arguments for budget command");
@@ -73,6 +94,9 @@ private void validateCommandFormat(RawCommand rawCommand) throws FinancialPlanne
         }
     }
 
+    /**
+     * Executes the budget command based on the specified operation.
+     */
     @Override
     public void execute() {
         assert command.equals("set") || command.equals("update") || command.equals("delete") ||
diff --git a/src/main/java/seedu/financialplanner/commands/Command.java b/src/main/java/seedu/financialplanner/commands/Command.java
index 135ccd4e4d..6b7b7e3e74 100644
--- a/src/main/java/seedu/financialplanner/commands/Command.java
+++ b/src/main/java/seedu/financialplanner/commands/Command.java
@@ -1,5 +1,8 @@
 package seedu.financialplanner.commands;
 
+/**
+ * Represents a generic command that can be inherited.
+ */
 public abstract class Command {
     public abstract void execute() throws Exception;
 }
diff --git a/src/main/java/seedu/financialplanner/commands/ExitCommand.java b/src/main/java/seedu/financialplanner/commands/ExitCommand.java
index 3c331475a6..03b5eb4285 100644
--- a/src/main/java/seedu/financialplanner/commands/ExitCommand.java
+++ b/src/main/java/seedu/financialplanner/commands/ExitCommand.java
@@ -2,6 +2,9 @@
 
 import java.util.ArrayList;
 
+/**
+ * Represents a command to exit the program.
+ */
 public class ExitCommand extends Command {
     public ExitCommand(RawCommand rawCommand) {
         if (!rawCommand.extraArgs.isEmpty()) {
diff --git a/src/main/java/seedu/financialplanner/commands/InvalidCommand.java b/src/main/java/seedu/financialplanner/commands/InvalidCommand.java
index 97bc73e9fa..68860c4c1a 100644
--- a/src/main/java/seedu/financialplanner/commands/InvalidCommand.java
+++ b/src/main/java/seedu/financialplanner/commands/InvalidCommand.java
@@ -2,10 +2,17 @@
 
 import seedu.financialplanner.utils.Ui;
 
+/**
+ * Represents a command for an invalid input.
+ */
 public class InvalidCommand extends Command {
     public InvalidCommand() {
     }
 
+    /**
+     * Executes the command to display an error message when an
+     * invalid input is received.
+     */
     @Override
     public void execute() {
         Ui.getInstance().showMessage("Unknown command. Please try again.");
diff --git a/src/main/java/seedu/financialplanner/commands/OverviewCommand.java b/src/main/java/seedu/financialplanner/commands/OverviewCommand.java
index 9aa2107a08..5242987f99 100644
--- a/src/main/java/seedu/financialplanner/commands/OverviewCommand.java
+++ b/src/main/java/seedu/financialplanner/commands/OverviewCommand.java
@@ -12,6 +12,9 @@
 import java.text.DecimalFormat;
 import java.util.ArrayList;
 
+/**
+ * Represents a command to display overview of user's financials.
+ */
 public class OverviewCommand extends Command {
     private static final CashflowList cashflowList = CashflowList.getInstance();
 
@@ -22,8 +25,11 @@ public OverviewCommand(RawCommand rawCommand) {
         }
     }
 
+    /**
+     * Executes the command and displays an overview of the user's financials.
+     */
     @Override
-    public void execute() throws Exception {
+    public void execute() {
         String balance = getBalance();
         String highestIncome = getHighestIncome();
         String highestExpense = getHighestExpense();
diff --git a/src/main/java/seedu/financialplanner/exceptions/FinancialPlannerException.java b/src/main/java/seedu/financialplanner/exceptions/FinancialPlannerException.java
index 387c7ddd06..bda7b2ab4b 100644
--- a/src/main/java/seedu/financialplanner/exceptions/FinancialPlannerException.java
+++ b/src/main/java/seedu/financialplanner/exceptions/FinancialPlannerException.java
@@ -1,5 +1,8 @@
 package seedu.financialplanner.exceptions;
 
+/**
+ * Represents exceptions specific to the Financial Planner.
+ */
 public class FinancialPlannerException extends Exception {
     public FinancialPlannerException(String message) {
         super(message);
diff --git a/src/main/java/seedu/financialplanner/storage/LoadData.java b/src/main/java/seedu/financialplanner/storage/LoadData.java
index 9a9810b014..cab7c5e59e 100644
--- a/src/main/java/seedu/financialplanner/storage/LoadData.java
+++ b/src/main/java/seedu/financialplanner/storage/LoadData.java
@@ -25,12 +25,22 @@
 import java.util.HashMap;
 import java.util.Scanner;
 
+/**
+ * Represents the loading of data from storage.
+ */
 public abstract class LoadData {
     private static final String FILE_PATH = "data/watchlist.json";
     private static final CashflowList cashflowList = CashflowList.getInstance();
     private static final Ui ui = Ui.getInstance();
 
 
+    /**
+     * Loads existing data from the storage file.
+     *
+     * @param filePath The file where the data is stored.
+     * @param date The current date.
+     * @throws FinancialPlannerException If there is an issue loading data from storage.
+     */
     public static void load(String filePath, LocalDate date) throws FinancialPlannerException {
         try {
             Scanner inputFile = new Scanner(new FileReader(filePath));
@@ -148,8 +158,14 @@ private static void handleCorruptedFile(String message) throws FinancialPlannerE
     }
 
     private static void loadBudget(String[] split) throws IllegalArgumentException {
-        double initial = Double.parseDouble(split[1].trim());
-        double current = Double.parseDouble(split[2].trim());
+        double initial;
+        double current;
+        try {
+            initial = Double.parseDouble(split[1].trim());
+            current = Double.parseDouble(split[2].trim());
+        } catch (IllegalArgumentException e) {
+            throw new IllegalArgumentException("Error parsing budget values.");
+        }
         if (initial == 0 && current == 0) {
             return;
         }
diff --git a/src/main/java/seedu/financialplanner/storage/SaveData.java b/src/main/java/seedu/financialplanner/storage/SaveData.java
index b11872d84e..17e49e4e86 100644
--- a/src/main/java/seedu/financialplanner/storage/SaveData.java
+++ b/src/main/java/seedu/financialplanner/storage/SaveData.java
@@ -12,9 +12,11 @@
 import java.io.FileWriter;
 import java.io.IOException;
 
+/**
+ * Represents the saving of data to storage.
+ */
 public abstract class SaveData {
     private static final String FILE_PATH = "data/watchlist.json";
-
     private static final CashflowList cashflowList = CashflowList.getInstance();
 
     public static void save(String filePath) throws FinancialPlannerException {
diff --git a/src/main/java/seedu/financialplanner/storage/Storage.java b/src/main/java/seedu/financialplanner/storage/Storage.java
index 95eeaf7100..ef491dc34e 100644
--- a/src/main/java/seedu/financialplanner/storage/Storage.java
+++ b/src/main/java/seedu/financialplanner/storage/Storage.java
@@ -8,6 +8,9 @@
 import java.nio.file.Paths;
 import java.time.LocalDate;
 
+/**
+ * Represents the saving and loading of data.
+ */
 public class Storage {
     private static Storage storage = null;
     private final Path path = Paths.get("data");
diff --git a/src/main/java/seedu/financialplanner/utils/Ui.java b/src/main/java/seedu/financialplanner/utils/Ui.java
index f3231e74de..d183ca2e45 100644
--- a/src/main/java/seedu/financialplanner/utils/Ui.java
+++ b/src/main/java/seedu/financialplanner/utils/Ui.java
@@ -12,6 +12,9 @@
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
+/**
+ * Represents the handling of user interactions.
+ */
 public class Ui {
     private static final Logger logger = Logger.getLogger("Financial Planner Logger");
     private static Ui ui = null;
diff --git a/src/test/java/seedu/financialplanner/commands/BudgetCommandTest.java b/src/test/java/seedu/financialplanner/commands/BudgetCommandTest.java
index 40e05cc636..019b0b4424 100644
--- a/src/test/java/seedu/financialplanner/commands/BudgetCommandTest.java
+++ b/src/test/java/seedu/financialplanner/commands/BudgetCommandTest.java
@@ -116,7 +116,7 @@ public void testInvalidBudget_throwsException() throws FinancialPlannerException
         try {
             BudgetCommand testBudgetExceedBalance = new BudgetCommand(Parser.parseRawCommand("budget set /b 500"));
         } catch (FinancialPlannerException e) {
-            assertEquals("Budget should be lower than total balance.", e.getMessage());
+            assertEquals("Budget should be lower than or equal to total balance.", e.getMessage());
         }
     }
 }