Free tool
Bulk NPI validator
Paste a list of NPIs, one per line, and check every number against the official checksum at once. Everything runs in your browser: nothing is uploaded.
One NPI per line, up to 1,000 lines. The number can sit anywhere in the line; blank lines are skipped.
How lines are read, and what the verdicts mean
Each line is scanned for its first run of exactly 10 digits, so whole rows pasted from a claim file or spreadsheet work as-is; surrounding text, phone numbers, and other columns are ignored.
- Valid: the tenth digit matches the Luhn checksum computed over the 80840 prefix plus the first nine digits. The number is well-formed, not necessarily assigned; confirm assignment with our NPI lookup.
- Invalid checksum: the tenth digit does not match. The expected check digit is shown; one mistyped digit is the usual cause.
- No 10-digit number found: the line contains no run of exactly 10 digits.
Checking a single number? The NPI validator shows the checksum math digit by digit.