AlarmBiller allows users to change the next check number.
Note: Unlike the next customer number, next invoice number, next vendor number, and next purchase order number, which are all found under Setup -> Under Company -> Defaults, this feature is in a different place.
Follow the steps below to change the next check number.
The next check number can be found under each bank.
In AlarmBiller go to Setup -> under Accounting -> Bank Accounts:

Click on the bank name in blue:

Click Edit.
Adjust the check number and click Save.

Note: if you do have multiple banks set up, the steps need to be repeated for each bank that needs the next check number adjusted.