Hello BenTam,

Allow me to jump in to this thread and provide clear steps on how to enter the check number.

1. Click on List and choose Chart of Accounts.
2. Double-click on the bank account.
3. Look for the check.
4. In the NUMBER/TYPE column, replace the To Print with the check number.
5. Press Enter on your keyboard and click on Yes when prompted to record the changes.

I've attached a screenshot for a visual guide. 

Let us know if you have any questions. Thanks!