How is the ISO 11649 check digit calculated?

The same ISO 7064 MOD-97-10 arithmetic used for IBAN check digits: append "RF00" to the reference, convert letters to numbers (A=10 … Z=35), divide by 97, and subtract the remainder from 98 to get the two check digits.

Does a valid RF reference confirm the invoice or payment is real?

No. A valid check digit only confirms the reference is formatted correctly — it does not verify that an invoice, order, or payment behind that reference actually exists. Only the issuer of the reference can confirm that.

RF Creditor Reference

Q: What is an RF creditor reference?

An RF creditor reference (ISO 11649 structured creditor reference) is a payment reference format with a built-in check digit. It starts with "RF", followed by two check digits, followed by up to 21 letters and digits. Banks and accounting systems can verify it automatically, unlike free-text invoice references.

Q: Where are RF references used?

RF references are common in SEPA credit transfers, especially in Finland, Sweden, Belgium, and other European countries where structured payment references are standard practice. They can be encoded in the payment reference field of a SEPA payment or an EPC payment QR code.

Generate an ISO 11649 structured creditor reference from an invoice or customer number, or validate one you already have. Same MOD-97 check digit math as an IBAN, run entirely in your browser.

Reference (invoice, order, or customer number)

What Is an RF Creditor Reference?

The structured creditor reference, defined by ISO 11649, is a payment reference format built for automated processing. Unlike a free-text invoice note, it carries its own check digits, so accounting software can catch a mistyped reference before a payment is reconciled against the wrong invoice. It always takes the shape RF## followed by up to 21 letters and digits — for example RF18 5390 0754 7034.

How the Check Digits Are Calculated

The algorithm is the same ISO 7064 MOD-97-10 arithmetic an IBAN uses for its own check digits, just rearranged:

Append: add the placeholder RF00 to the end of the reference.
Convert letters: replace each letter with its numeric equivalent (A=10, B=11, …, Z=35).
MOD 97: compute the remainder when the resulting number is divided by 97.
Subtract from 98: the check digits are 98 − remainder, zero-padded to two digits, prefixed with RF.

Where Is It Used?

RF references are widely used in SEPA credit transfers, particularly in Finland, Sweden, Belgium and other European countries where structured payment references are the norm rather than free text. The reference goes in the payment reference field of a SEPA transfer, or in the reference field of a payment QR code — you can check what any scanned QR actually carries with the payment QR decoder.

What This Does Not Verify

A valid check digit confirms the reference is formatted correctly — not that an invoice, order, or payment behind it actually exists. Only the party that issued the reference can confirm that. To validate the IBAN a payment is going to, use the full IBAN checker.

Sources & References

ISO 11649:2009: the official standard defining the structured creditor reference and its scope.
Finance Finland (Finanssiala): Introduction of the Global Structured Creditor Reference (RF) in Finnish Companies: confirms the check digit algorithm is identical to the IBAN check digit algorithm, the 21-character maximum for the reference part, and the four-digit print grouping with no leading zeros used on this page.

Last updated: August 2026