diff --git a/docs/UserGuide.md b/docs/UserGuide.md
index abd9fbe891..d9cbd084b8 100644
--- a/docs/UserGuide.md
+++ b/docs/UserGuide.md
@@ -2,41 +2,97 @@
 
 ## Introduction
 
-{Give a product intro}
+StockMaster is a platform aimed at helping SMEs track and organise their inventory.
 
 ## Quick Start
 
 {Give steps to get started quickly}
 
 1. Ensure that you have Java 11 or above installed.
-1. Down the latest version of `Duke` from [here](http://link.to/duke).
+2. Download the latest version of `StockMaster` from [here](http://link.to/duke).
+3. 
 
 ## Features 
 
 {Give detailed description of each feature}
 
-### Adding a todo: `todo`
-Adds a new item to the list of todo items.
+### Adding an item: `add`
+Adds a new item to the list of items.
 
-Format: `todo n/TODO_NAME d/DEADLINE`
+Format: `add ITEM_NAME qty/ITEM_QUANTITY [cat/CATEGORY]`
 
-* The `DEADLINE` can be in a natural language format.
-* The `TODO_NAME` cannot contain punctuation.  
+* `CATEGORY` is an optional field. If blank, it will default to `N/A`.
 
 Example of usage: 
+```
+add Apples qty/50
+add Phone qty/5 cat/Electronics
+```
 
-`todo n/Write the rest of the User Guide d/next week`
+### Deleting an item: `del`
+Deletes the item from the list of items.
 
-`todo n/Refactor the User Guide to remove passive voice d/13/04/2020`
+Format: `del ITEM_NAME`
+
+Example of usage:
+```
+del Apples
+```
+
+### Editing an item: `edit`
+Edits the quantity of the item.
+
+Format: `edit ITEM_NAME qty/NEW_QUANTITY`
+
+Example of usage:
+```
+edit Apples qty/10
+edit Phone qty/0
+```
+
+### Listing all items: `list`
+Lists all stored items.
+
+Format: `list [cat/CATEGORY]`
+
+* `CATEGORY` is an optional field. By default, it will list all the stored items.
+
+Example of usage:
+```
+list
+list Electronics
+```
+
+### List all available commands: `help`
+Lists all commands as per the command summary below.
+
+Format: `help [c/COMMAND]`
+
+* `COMMAND` is optional. Specifying the command will give a more comprehensive
+  description of the command.
+
+Example of usage:
+```
+help
+help c/add
+```
+
+
+### Closing the app: `exit`
+Saves and closes the app safely.
+
+Format: `exit`
 
 ## FAQ
 
 **Q**: How do I transfer my data to another computer? 
 
-**A**: {your answer here}
+**A**: Simply copy and paste the saved folder that is created upon launch of 
+the application.
 
 ## Command Summary
 
-{Give a 'cheat sheet' of commands here}
-
-* Add todo `todo n/TODO_NAME d/DEADLINE`
+* Add new item: `add Apples qty/10 cat/Food`
+* Delete an item: `delete Apples`
+* List all items: `list`
+* List all commands: `help`
\ No newline at end of file
diff --git a/src/main/java/command/Command.java b/src/main/java/command/Command.java
index 41649ed097..a71e7f8779 100644
--- a/src/main/java/command/Command.java
+++ b/src/main/java/command/Command.java
@@ -1,6 +1,8 @@
 package command;
 
-public abstract class Command {
+import exceptions.CommandFormatException;
 
-    public abstract void execute();
+public abstract class Command  {
+
+    public abstract void execute() throws CommandFormatException;
 }
diff --git a/src/main/java/command/DeleteCommand.java b/src/main/java/command/DeleteCommand.java
index 2da1c3483d..7ce9312919 100644
--- a/src/main/java/command/DeleteCommand.java
+++ b/src/main/java/command/DeleteCommand.java
@@ -1,7 +1,9 @@
 package command;
 
+import exceptions.CommandFormatException;
 import item.Item;
 import itemlist.Itemlist;
+import parser.CommandType;
 import storage.Storage;
 
 public class DeleteCommand extends Command {
@@ -12,7 +14,7 @@ public DeleteCommand(String itemName) {
         this.itemName = itemName;
     }
 
-    public void execute() {
+    public void execute() throws CommandFormatException {
         int index = -1;
         for (Item item : Itemlist.getItems()) {
             if (item.getItemName().toLowerCase().equals(itemName)) {
@@ -22,6 +24,7 @@ public void execute() {
         }
         if (index == -1) {
             //throw exception;
+            throw new CommandFormatException(CommandType.DEL);
         } else {
             Itemlist.deleteItem(index);
         }
diff --git a/src/main/java/seedu/duke/Duke.java b/src/main/java/seedu/duke/Duke.java
index 9af6f9d0f9..8d14fe25b9 100644
--- a/src/main/java/seedu/duke/Duke.java
+++ b/src/main/java/seedu/duke/Duke.java
@@ -2,6 +2,7 @@
 
 import command.Command;
 import command.ExitCommand;
+import exceptions.CommandFormatException;
 import parser.Parser;
 import ui.TextUi;
 
@@ -17,17 +18,17 @@ public class Duke {
     /**
      * Main entry-point for the java.duke.Duke application.
      */
-    public static void main(String[] args) throws IOException {
+    public static void main(String[] args) throws IOException, CommandFormatException {
         new Duke().run();
     }
 
-    public void run() throws IOException {
+    public void run() throws IOException, CommandFormatException {
         ui.showWelcomeMessage("1.0", "./StockMasterData.txt");
         this.normalOperation();
         ui.showGoodByeMessage("./StockMasterData.txt");
     }
 
-    private void normalOperation() throws IOException {
+    private void normalOperation() throws IOException, CommandFormatException {
         String userInput;
         do {
             userInput = ui.getUserInput();
diff --git a/src/test/java/command/CommandTest.java b/src/test/java/command/CommandTest.java
new file mode 100644
index 0000000000..e740812c25
--- /dev/null
+++ b/src/test/java/command/CommandTest.java
@@ -0,0 +1,13 @@
+package command;
+
+import org.junit.jupiter.api.Test;
+
+public class CommandTest {
+    private Command command;
+
+    @Test
+    public void command_invalidCommand_throwsError() {
+
+    }
+
+}