Hello there, @accounting35.
It's my pleasure to help you today so you'll be able to receive a notification or be warned if there's duplicate transactions/information created.
You may turn on a specific settings to be warned if duplicate check number and duplicate number is used. Let me show you how.
- Go to the Gear icon.
- Select Account and Settings under Your Company.
- Go to the Advanced tab.
- Click on Other preferences.
- Put a check-mark on Warn if duplicate check number is used and Warn if duplicate bill number is used.
- Click Save and click Done.
After turning it on, you'll be warned automatically if you've entered transactions with the same information. Don't hesitate to add a comment below if you have any other concerns, we're always here to help. Have a wonderful day!