Invoice number gap checker
Find duplicate invoice identifiers and internal sequence gaps without uploading your records.
One identifier per line, up to 20000 identifiers, 2000000 characters and 200 characters per identifier. End identifiers in 1 to 30 ASCII digits. Prefix, digit width and explicit reset section determine groups. Leading zeros and case are preserved. Missing ranges stay compact even for huge numeric gaps. Checks observed endpoints only; not an accounting completeness audit. Local worker with 10-second timeout. Full JSON and formula-protected CSV include every identifier, duplicate, invalid line, range and assumption. Up to 1,000,000 characters. Review the settings before running.
Your result
How to use Invoice number gap checker
- Paste one invoice identifier per line.
- Choose whether blank lines continue numbering or reset it for a new period.
- Review compact missing ranges and summary counts. Download the full report for duplicates and invalid lines.
Useful next steps
Group sequences deliberately
INV-001 and INV-1 have different digit widths and are checked separately. Prefixes are case-sensitive. If the same prefix restarts each month, separate periods with a blank line and choose reset mode. Dates in prefixes are not interpreted.
A gap needs context
Cancelled, reserved, migrated or separately issued numbers can create legitimate gaps. This tool finds numbering patterns between the first and last observed values. It does not establish that an invoice is missing or infer misconduct.