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# Validating IBAN bank account numbers

> Validate IBAN account numbers by checking structure, country-specific length, and bank country match.

When providing beneficiary account data during payment creation or during RFIs,
OFIs may need to submit IBAN (International Bank Account Number) values that
follow a specific format. You can validate these numbers by checking their
structure, their country-specific length, and their country code against the
bank country.

An IBAN has 15 to 34 alphanumeric characters and follows the ISO 13616 standard.
Its structure is:

* First 2 characters: country code (uppercase letters, ISO 3166-1 alpha-2)
* Next 2 characters: check digits (digits)
* Remaining 11 to 30 characters: country-specific BBAN (Basic Bank Account
  Number), alphanumeric

IBANs are validated by their format, their country-specific length, and by
matching their country code against `BANK_COUNTRY`.

## Country-specific length

Each IBAN-issuing country has a fixed length defined by the ISO 13616 registry.
The following table lists the expected lengths:

| Country code | Country                | Length |
| ------------ | ---------------------- | ------ |
| `AD`         | Andorra                | 24     |
| `AE`         | United Arab Emirates   | 23     |
| `AL`         | Albania                | 28     |
| `AT`         | Austria                | 20     |
| `AZ`         | Azerbaijan             | 28     |
| `BA`         | Bosnia and Herzegovina | 20     |
| `BE`         | Belgium                | 16     |
| `BG`         | Bulgaria               | 22     |
| `BH`         | Bahrain                | 22     |
| `BI`         | Burundi                | 27     |
| `BR`         | Brazil                 | 29     |
| `BY`         | Belarus                | 28     |
| `CH`         | Switzerland            | 21     |
| `CR`         | Costa Rica             | 22     |
| `CY`         | Cyprus                 | 28     |
| `CZ`         | Czech Republic         | 24     |
| `DE`         | Germany                | 22     |
| `DJ`         | Djibouti               | 27     |
| `DK`         | Denmark                | 18     |
| `DO`         | Dominican Republic     | 28     |
| `EE`         | Estonia                | 20     |
| `EG`         | Egypt                  | 29     |
| `ES`         | Spain                  | 24     |
| `FI`         | Finland                | 18     |
| `FK`         | Falkland Islands       | 18     |
| `FO`         | Faroe Islands          | 18     |
| `FR`         | France                 | 27     |
| `GB`         | United Kingdom         | 22     |
| `GE`         | Georgia                | 22     |
| `GI`         | Gibraltar              | 23     |
| `GL`         | Greenland              | 18     |
| `GR`         | Greece                 | 27     |
| `GT`         | Guatemala              | 28     |
| `HN`         | Honduras               | 28     |
| `HR`         | Croatia                | 21     |
| `HU`         | Hungary                | 28     |
| `IE`         | Ireland                | 22     |
| `IL`         | Israel                 | 23     |
| `IQ`         | Iraq                   | 23     |
| `IS`         | Iceland                | 26     |
| `IT`         | Italy                  | 27     |
| `JO`         | Jordan                 | 30     |
| `KW`         | Kuwait                 | 30     |
| `KZ`         | Kazakhstan             | 20     |
| `LB`         | Lebanon                | 28     |
| `LC`         | Saint Lucia            | 32     |
| `LI`         | Liechtenstein          | 21     |
| `LT`         | Lithuania              | 20     |
| `LU`         | Luxembourg             | 20     |
| `LV`         | Latvia                 | 21     |
| `LY`         | Libya                  | 25     |
| `MC`         | Monaco                 | 27     |
| `MD`         | Moldova                | 24     |
| `ME`         | Montenegro             | 22     |
| `MK`         | North Macedonia        | 19     |
| `MN`         | Mongolia               | 20     |
| `MR`         | Mauritania             | 27     |
| `MT`         | Malta                  | 31     |
| `MU`         | Mauritius              | 30     |
| `NI`         | Nicaragua              | 28     |
| `NL`         | Netherlands            | 18     |
| `NO`         | Norway                 | 15     |
| `OM`         | Oman                   | 23     |
| `PK`         | Pakistan               | 24     |
| `PL`         | Poland                 | 28     |
| `PS`         | Palestinian Territory  | 29     |
| `PT`         | Portugal               | 25     |
| `QA`         | Qatar                  | 29     |
| `RO`         | Romania                | 24     |
| `RS`         | Serbia                 | 22     |
| `RU`         | Russia                 | 33     |
| `SA`         | Saudi Arabia           | 24     |
| `SC`         | Seychelles             | 31     |
| `SD`         | Sudan                  | 18     |
| `SE`         | Sweden                 | 24     |
| `SI`         | Slovenia               | 19     |
| `SK`         | Slovakia               | 24     |
| `SM`         | San Marino             | 27     |
| `SO`         | Somalia                | 23     |
| `ST`         | São Tomé and Príncipe  | 25     |
| `SV`         | El Salvador            | 28     |
| `TL`         | Timor-Leste            | 23     |
| `TN`         | Tunisia                | 24     |
| `TR`         | Turkey                 | 26     |
| `UA`         | Ukraine                | 29     |
| `VA`         | Vatican City           | 22     |
| `VG`         | British Virgin Islands | 24     |
| `XK`         | Kosovo                 | 20     |
| `YE`         | Yemen                  | 30     |

Some overseas territories use their parent country's IBAN format:

| Territory code | Territory                   | Parent | Length |
| -------------- | --------------------------- | ------ | ------ |
| `AX`           | Åland Islands               | `FI`   | 18     |
| `BL`           | Saint Barthélemy            | `FR`   | 27     |
| `EA`           | Ceuta and Melilla           | `ES`   | 24     |
| `GF`           | French Guiana               | `FR`   | 27     |
| `GG`           | Guernsey                    | `GB`   | 22     |
| `GP`           | Guadeloupe                  | `FR`   | 27     |
| `IC`           | Canary Islands              | `ES`   | 24     |
| `IM`           | Isle of Man                 | `GB`   | 22     |
| `JE`           | Jersey                      | `GB`   | 22     |
| `MF`           | Saint Martin (French part)  | `FR`   | 27     |
| `MQ`           | Martinique                  | `FR`   | 27     |
| `NC`           | New Caledonia               | `FR`   | 27     |
| `PF`           | French Polynesia            | `FR`   | 27     |
| `PM`           | Saint Pierre et Miquelon    | `FR`   | 27     |
| `RE`           | Réunion                     | `FR`   | 27     |
| `SJ`           | Svalbard and Jan Mayen      | `NO`   | 15     |
| `TF`           | French Southern Territories | `FR`   | 27     |
| `WF`           | Wallis and Futuna Islands   | `FR`   | 27     |
| `YT`           | Mayotte                     | `FR`   | 27     |

## Cross-field validation with bank country

When both IBAN and `BANK_COUNTRY` are provided, the IBAN's country code (first 2
characters) must match `BANK_COUNTRY`. Overseas territories resolve to their
parent country before the check. For example, an IBAN starting with `GG`
(Guernsey) is treated as `GB`.

## Example

The following is an example of validating the IBAN `GB82WEST12345698765432`:

**Structure**

* Country code: `GB` (United Kingdom)
* Check digits: `82`
* BBAN: `WEST12345698765432` (18 characters)
* Total length: `22` (matches the fixed length for `GB`)

**Cross-field check**

* IBAN country code: `GB`
* `BANK_COUNTRY`: `GB` (matches)