How do I deal with a credit on my Discover Card bill when I split the transactions into categories

I can help you through the process of recording a credit card credit, MtTSA.

You can manually enter a credit card credit in QuickBooks and exclude the bank download transactions in the Banking page to avoid duplicates. Let me show you how to create a credit card credit. 

1. Log in to QuickBooks Online.
2. From the +New button, select Credit card credit.
3. Select the credit card.
4. Enter an income account and the credit amount.
5. Click Save and close.

To exclude the bank downloaded transaction, just go to the Banking page and select the transaction. Click Exclude.

On the other hand, if you want to add the bank transaction. you can manually Find Match and Resolve the difference to enter the credit. 

Check out this page that will help you manage bank downloaded transactions: Categorize and Match Online Bank Transactions in QuickBooks Online. 

Let me know if you have other questions. You take care and have a great day.