The Accounts Payable and Payroll use the Last AP Check and Last PR Check on the Cash Management bank account to determine the next check number. When you print checks in Accounts Payable or Payroll, the check number is one digit higher than the number in the Last AP Check or Last PR Check section. If these boxes contain incorrect information, you may receive an error message, or incorrect check numbers will prefill for the next check number when you print checks. If Payroll and Accounts Payable use the same Cash Management bank account, the Last AP Check box in Cash Management (Setup, Bank Accounts, Last Transactions) may update incorrectly when a Payroll check is voided and reissued with the same check number.
Note: If the sequence was altered in AP, it was likely due to the setting: Manual check updates Last Check number check box, in AP settings. See How do I prevent manual checks from changing my check number sequence?