Duplicate Check Numbers
What does "Check is not valid, either assign a different number or clear the existing number to continue," mean?
In accordance with best accounting practices, the 2017 first quarter release included an enhancement that prevents duplicate alpha-numeric check numbers within the Assign Check Number process. Previously only duplicate *numeric* check numbers were prevented.
For instance, you can no longer use **ACH** as the reference for multiple transactions. Instead, you could use **ACH** followed by the date with no dashes: **ACH20170331**. If you had multiple transactions you may follow them with a letter such as a,b,c... Example: ACH20170331a, ACH20170331b, etc. (Where the date is 3/31/2017).
Using this date format means that when sorting by check number all of your checks will be together by year instead of by month (IE all 2017 checks instead of all January checks regardless of year).