Why the error occurs
This error occurs when a payment on a bill in Bill.com is trying to sync to QuickBooks Online, but the bill is already marked as paid in QuickBooks Online.
How to fix the error
Option 1: Void the payment in QuickBooks Online
The easiest solution to this error is to void the payment in QuickBooks Online and sync again, so the payment in Bill.com syncs to QuickBooks Online.
Option 2: Keep the payment in QuickBooks online
If you need to keep the payment you recorded in QuickBooks Online, contact Customer Support to clear the error.
Note: If you made a live payment on the bill in Bill.com, be sure the payment account listed on the payment in QuickBooks Online is Money Out Clearing to avoid an account imbalance.