When the voucher numbering method in your voucher is not set to automatic, this error occurs. Read on for the solution.
Bank entries are posted under Payment, Receipt, or Contra vouchers. If any of these use Manual or Automatic (Manual Override) voucher numbering instead of Automatic, Tally will show this error: "Voucher Number cannot be left blank."
To check the reason for this error, refer to this guide: Why transactions failed to sync in Tally
The image above shows the error from the Tally.imp file
Step 1: Press Alt+Y (Data) → All Exceptions Step 2: A report opens listing import and sync issues Step 3: Clear/Delete all exception entries related to this error