Thank you for joining the thread, @payments9. 

Allow me to guide you on how you can void a paper check in QuickBooks Online (QBO).

You can follow the steps below:
 

1. On the left panel, go to Transactions.
2. Select Chart of accounts.
3. Click on the View register.
4. Locate the check you want to void.
5. Click More then select Void.

Note: Dismiss any warning prompts by confirming the voiding process. You may also check this article for more detailed info: Void or cancel contractor payments

Furthermore, if you want to learn more on how to record a refund or credit from a vendor, you can scan through this article: Enter vendor credits and refunds in QuickBooks Online

If you need additional assistance with recording and managing paper checks in QuickBooks, please don't hesitate to leave a comment below. I'm ready to help 24/7. Take care!