Hi carol96.

Thanks for posting in the Community!

You can assign a GST code to a split transaction in QuickBooks Online. Make sure your GST is turned on and set up to add GST codes to your bank/credit transactions.

Here's how to split transactions:

1. Click on the Banking/Transactions tab.
2. Click on the For Review tab.
3. Click the downloaded transaction.
4. Click on Split next to the Add button.
5. On the next screen, fill out each field and there should be a GST column to assign the GST code.
6. Click on Apply and accept.

If this is what you've done to categorise the split transaction. We'd recommend logging in using a new incognito window or a different web browser when trying to categorise your bank transaction to isolate the situation.

You can check this article to learn more about how to

Categorise and match online bank transactions in QuickBooks Online.

Feel free to reply on this thread if you have any other questions. Have a nice day!