Hi there, @orangzeb.

You need to turn on class tracking in QuickBooks Online Plus and Advanced to organize the transactions by class. If you're using QuickBooks Simple Start and Essentials, I suggest upgrading your subscription. I'll show you how:

1. Go to the Settings ⚙ and choose Account and Settings.
2. Select the Billing & Subscription menu.
3. In the QuickBooks Online section, select Upgrade. 
4. Choose either QuickBooks Plus or Advanced, and select Upgrade.
5. Confirm your payment information, and click Save.

Once done, you can now assign classes to transactions by turning on the class tracking feature.

Here's how:

1. Select Settings ⚙ and choose Account and Settings.
2. Choose Advanced, then click on  Edit ✎ in the Categories section.
3. Select Track classes.
4. Click the Assign classes ▼ dropdown, then select One to entire transaction or One to each row in transaction.
5. Select Save, then Done.

You can visit this article to guide you on how to add, delete, or restore a class in QuickBooks Online: Create and manage classes in QuickBooks Online.

Click the Reply button if you have additional queries about assigning classes to transactions. I'll be here to help.