To resolve inconsistencies in bill numbers being generated, either you can modify each voucher and correct the voucher numbering after set the voucher numbering as Manual or Run the renumbering process by using these steps:
Step 1: Go to Administration and click on configuration.
Step 2: Choose the Voucher Series Configuration option and select the voucher type such as sale, purchase, etc. Then, select the voucher series and click on Voucher Numbering.
Step 3: Choose the Numbering Type as either Automatic. Then, verify the prefix, suffix, and Starting No. as per your needs and click on OK.
Step 4: Then a window will appear of renumbering, press yes and then check.
Note: Take backup of your data before running this process.