# NPI Validation Tool

## NPI Validation Rules

The National Provider Indentifier (NPI) is 10-position all-numeric identification number assigned by the National Plan and Provider Enumeration System (NPPES) to uniquely identify a health care provider.

Characteristics of NPI numbers:

• NPI numbers consist of 9 numeric digits followed by one numeric check digit, for a total of 10 numeric digits.
• The NPI numbers check digit is calculated using the ISO standard Luhn Formula algorithm for Modulus 10 "double-add-double".
• NPI numbers are compatible with ISO identification card standards for a card issuer identifier when using the 80840 prefix.
• NPI numbers have no embedded intelligence.
• NPI numbers do not require translation before application of the check digit algorithm and thus uses the full ability of the check digit algorithm to detect keying errors.

How to calculate the NPI check digit?

The following NPI validation example will show you step by step how to apply ISO standard Luhn algorithm for NPI number validation:

### NPI Validation Step 1

Take the first 9 digits of the NPI number and double the value of alternate digits beginning with the rightmost digit.

Example NPI to validate: 1134296023

NPI Digit Position Action Operation Result
1Double the 1st digit1 x 22
2No Action11
3Double the 3rd digit3 x 26
4No Action44
5Double the 5th digit2 x 24
6No Action99
7Double the 7th digit6 x 212
8No Action00
9Double the 9th digit2 x 24
10No Action - Check Digit33

### NPI Validation Step 2

Add the individual digits of the products resulting from step 1 to the unaffected digits from the original NPI number and add the constant number 24.

Add the Result Digits from Step 1 plus Constant 24 Result
2+1+6+4+4+9+1+2+0+4+24=57

### NPI Validation Step 3

Subtract the total obtained in step 2 from the next higher number ending in zero, this is the check digit. If the number obtained in step 2 ends in zero, the check digit is zero.

Result from Step 2 Round up Number Validation Action Result Check Digit
576060-573

The NPI is valid because the result check digit 3 matches the last digit of the NPI number after applying the Luhn validation algorithm.