The ISO 7064 Mod 97-10 Check Character Algorithm Explained

Compiled & reviewed by the EntityCodes Editorial Team (Tech Labs FZ LLC) · Data verified: 2026-06-28

The ISO 7064 Mod 97-10 checksum algorithm validates the structure of 20-character Legal Entity Identifiers by verifying check digits.

Mathematical Steps of the Check Character System

The check characters in characters 19 and 20 of the LEI code verify formatting accuracy ^[1]. To validate an LEI using the ISO 7064 Mod 97-10 algorithm, follow these mathematical steps:

Convert all letters in the 20-character string to numbers where A = 10, B = 11, C = 12, ..., Z = 35.
Move the check digits (characters 19 and 20) to the end of the newly generated numerical string.
Compute the modulo 97 of the resulting integer.
Assert that the remainder equals exactly 1. If the remainder is 1, the format is valid ^[1].

Our client-side validator implements this algorithm in pure Javascript to perform instant validation checks on target LEIs without querying external APIs.

Global Financial Standards & LEI Mandates

To support the core compliance tasks detailed in this guide on The ISO 7064 Mod 97-10 Check Character Algorithm Explained, compliance officers and corporate attorneys must consult several international financial standards. Reference data for all active identifiers is published in the Global Legal Entity Identifier Foundation (GLEIF) GLEIF Golden Copy and Reference Data Registry. The code's alphanumeric structure is specified by the International Organization for Standardization (ISO) ISO 17442:2020 Financial services — Legal Entity Identifier (LEI), and its mathematical integrity is checked using the check digits standard International Organization for Standardization (ISO) ISO 7064:2003 Check character systems. The systemic oversight of these codes was established following the recommendation of the Financial Stability Board (FSB) LEI Governance and Implementation Progress Reports. Swap trade reporting regulations require active codes under the Commodity Futures Trading Commission (CFTC) Swap Data Recordkeeping and Reporting Requirements (LEI Mandate). Investment company registration forms are regulated by the U.S. Securities and Exchange Commission (SEC) Form N-PORT and Investment Company LEI requirements. European trading rules enforce a strict 'no-LEI, no-trade' policy under European Securities and Markets Authority (ESMA) MiFID II/MiFIR LEI requirements and 'No LEI, No Trade' policy. Regulatory committees monitor standard implementations following the Regulatory Oversight Committee (ROC) ROC Committee Guidelines for Global LEI System. The Federal Reserve details U.S. banking expectations in the Federal Reserve Board (FRB) Supervision and Regulation Letter SR 14-7 on LEI Expectations, and LOU accreditation standards are managed via the Global Legal Entity Identifier Foundation (GLEIF) GLEIF Accreditation Requirements for Local Operating Units (LOUs).

💡 Expert Guidance: Modulo 97 Checksum Validation Failure

Implementing a basic modulo-97 calculation without converting characters to their correct numeric equivalents (A=10 through Z=35) is a common coding error in financial software. The ISO 7064 Mod 97-10 routine requires running the algorithm exactly to confirm if a character transcription error occurred during input.

Frequently Asked Questions

How does Mod 97-10 detect entry errors? ▾

The algorithm detects single character swaps, adjacent transpositions, and digit omissions by ensuring the modulo of the string is 1.

Is the check digit algorithm public? ▾

Yes. The Mod 97-10 check character system is standardized under ISO 7064 and is freely available for implementation.

What is the ISO 7064 Mod 97-10 check character system? ▾

The ISO 7064 Mod 97-10 system is a mathematical checksum routine that calculates two check digits to detect transcription errors, character transpositions, and formatting issues in alphanumeric codes.

How are alphanumeric characters converted to numbers in Mod 97-10 calculations? ▾

Alphanumeric characters are converted to numbers by replacing each letter with its corresponding two-digit numeric value (where A=10, B=11, C=12, ..., Z=35) to create a pure integer.

What is the mathematical modulus formula used to validate an LEI? ▾

To validate an LEI, you convert the string to a numeric value, perform a modulo 97 division, and assert that the remainder is exactly `1`. If the remainder is `1`, the checksum is valid.

Why is Mod 97-10 preferred over simpler checksums like Mod 10? ▾

Mod 97-10 is preferred because it can detect over 99.9% of transposition errors, character insertions, and substitution errors, making it much more reliable than simpler checksum algorithms.

What is the formula to calculate the check digits for a new LEI? ▾

To calculate check digits, you append `00` to the 18-digit string, compute the remainder modulo 97, subtract that remainder from 98, and format the result as a two-digit string.

Are IBAN bank numbers validated using the same Mod 97 algorithm? ▾

Yes, the International Bank Account Number (IBAN) format utilizes the identical ISO 7064 Mod 97-10 checksum algorithm to validate bank routing and account numbers globally.

Does the Mod 97-10 algorithm catch letter-to-number swap errors? ▾

Yes, because the conversion step replaces letters with distinct two-digit numbers, any swap between letters and numbers shifts the modular remainder, catching the error.

Can I implement the ISO 7064 check in client-side Javascript? ▾

Yes, because large integer division is lossy in standard Javascript floating point math, you must implement the modulus using big integer arithmetic (`BigInt`) or block-by-block division.