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Issuer Identification Number (IIN)
Frequently Asked Questions

What is an IIN?

An IIN is an Issuer Identification Number, sometimes known as ISO or ATM BIN number. This is a 8-digit number that uniquely identifies transactions for a credit union’s ATM card program.

A 6-digit IIN is now an 8-digit IIN?

You may or may not know, ISO/IEC 7812-1 was revised to extend the length of the IIN from a fixed-length numeric of 6-digits to an 8-digit numeric value. This revision to the standard was formally published in January 2017. Any new applications submitted to the Registration Authority are now fulfilled as 8-digit IINs. The new Important Information Fact Sheet outlines the new 8-digit format. Even though your processor may not be ready for this change, your credit union is being assigned an 8-digit IIN. It is important to note that if you intend to implement your card program using the first 6-digits of that 8-digit IIN, you are prohibited from using any numbers in the 7th and 8th position starting with 01 through 99. That means your account ranges all MUST begin with 00.

For all credit unions assigned an IIN prior to January 2017, your 6-digit IIN has been grandfathered in. Your IIN will now become 100 numbers. Example: IIN 123456 now becomes 12345600 – 12345699. The reasoning is your processor probably already used the 7th and 8th positions with numbers 00-99.

CUNA Strategic Services (CSS) doesn't process my ATM cards.  Why did they issue my IIN?

Card processors are not allowed to issue IINs. At the request of credit unions, CSS became an authorized block holder and began issuing these numbers in the early 1980s. CSS is not the only authorized block holder, so it is possible that your credit union may have other IINs not issued by CSS. For example, Visa or MasterCard may have issued an IIN for your debit card program. 

How much is the annual maintenance fee?

The 2020 annual maintenance fee is $77 for each IIN issued by CSS that is still being actively used by your credit union for its ATM card program. This fee helps cover the cost for maintaining a database relative to the assignment of each IIN to credit unions since the early 1980s. We ensure that each IIN is unique to each credit union and we are required to notify the registration authority on a monthly basis of each IIN assigned, in addition to any deletions and/or changes such as mergers and name changes. 

Didn't I pay this fee already in 2020?

We send the invoice during the second quarter of the billing year. IINs relinquished during 2020 do not incur an annual maintenance fee. This is the first invoice for the 2020 maintenance fee, so you may have paid the 2019 fee in 2020.

How do I pay the bill?

Check, debit or credit are acceptable payment methods.  Please send the invoice along with a check payable to Credit Union National Association, Inc. and mail it to:

Credit Union National Association, Inc.
P.O. Box 78546
Milwaukee, WI 53278-0546 

You may contact Member Experience at 800-356-9655, press option 0 to pay via debit or credit card or for general assistance.

What happens if I don't pay the fee?

Your credit union's IIN will be listed as inactive and be eligible for use by another credit union. 

What if I have an IIN that is no longer being used by our credit union?

If an IIN is inactive due to a merger or other reasons, you must relinquish the number by emailing the invoice and a letter (on credit union letterhead) with the following information:

  1. The IIN to be relinquished
  2. Reason for relinquishing the number (e.g., processor change, merger, liquidation). If it is due to a merger, provide the name of the credit union for which the number was originally issued and the date of the merger or liquidation.
  3. The date the IIN may be deactivated
  4. Signed by an officer of the credit union
  5. The letter should be addressed to, but not mailed to:

ISO Registrar
American Bankers Association
1120 Connecticut Avenue, NW
Washington, DC 20036

     6. On the invoice, circle the IIN(s) being relinquished. Email the letter and invoice to Miranda Gibson at

We will send you a corrected invoice if there are any remaining active numbers. Once a relinquish letter for an IIN is received, future invoices will be adjusted to remove the annual fee for the relinquished IIN and the registrar will be notified that the number is available for use by another credit union.