Good day, @accounts64.
Thanks for reaching out to us in the Community. I'm here to share some information about reversing the payment entered twice in QuickBooks Online (QBO).
You can create a journal entry (JE) to offset the other payment. However, before we proceed with the steps, I highly suggest consulting your accountant or accounting professional for guidance on which account receives the debit and credit side of the transaction.
To create a JE, here's how:
1. Go to the Plus icon at the upper, then pick Journal Entry under Other column.
2. Enter a Journal Date, then on the first line, choose an account on the Accounts column.
3. Enter the payment amount in the Debits or Credits column.
4. Continue to enter distribution lines until the sum of the Debit column and Credit column entries are equal.
5. Hit Save.
For additional information, check out this article: Create a journal entry.
That should do it. Please let me know how it goes in the comment section. I'm only a few clicks away if you need anything else. Cheers!