IBAN format · ES

Spain IBAN format: 24 characters.

Spain IBANs have 24 characters: the country code ES, two check digits and a 20-character BBAN, the national account number, laid out as 4!n4!n1!n1!n10!n.

Spain IBAN structure

ES9121000418450200051332

Country code: ES
Check digits: 91
Bank code: 2100
Branch code: 0418
National check digits: 45
Account: 0200051332

Parts of a Spain IBAN and their positions
Positions	Part	In the example
1–2	Country code	ES
3–4	Check digits	91
5–8	Bank code	2100
9–12	Branch code	0418
13–14	National check digits	45
15–24	Account	0200051332

The BBAN, segment by segment

The registry writes the BBAN in SWIFT notation: n is a digit, a an upper-case letter, c a letter or digit, and the ! means a fixed length. 4!n4!n1!n1!n10!n reads:

The Spain BBAN format, segment by segment
Positions	Notation	Holds	Example
5–8	4!n	4 digitsBank code (entidad)	2100
9–12	4!n	4 digitsBranch code (oficina)	0418
13	1!n	1 digitCheck digit for bank and branch	4
14	1!n	1 digitCheck digit for the account	5
15–24	10!n	10 digitsAccount number	0200051332

Spain IBAN example

ES91 2100 0418 4502 0005 1332 is the sample the SWIFT IBAN Registry publishes for Spain: a well-formed IBAN for showing the format, not a real account. Written electronically it has no spaces (ES9121000418450200051332); on paper it is printed in groups of four.

Its check digits, worked through with ISO 7064 mod 97-10:

Move the country code and check digits to the end
21000418450200051332ES91
Replace each letter with two digits (A = 10 … Z = 35)
E = 14, S = 28
21000418450200051332142891
Divide that number by 97 and keep the remainder
Remainder 1. A valid IBAN always leaves 1, so the check digits are right.
Where the check digits come from
Put 00 in their place (ES00…), repeat steps 1–3: remainder 7. The check digits are 98 − 7 = 91.

SEPA

Spain is in the Single Euro Payments Area, so SEPA credit transfers and direct debits can reach ES IBANs; whether a given bank takes part is up to that bank.

What the format can and can’t tell you

Valid means the structure and check digits are right — not that the account exists or can receive payments.
National check digits inside the BBAN (e.g. the French RIB key, or the Spanish, Belgian and Italian CIN digits) are not verified.
Bank and branch codes are read from their positions; they are not looked up in a bank directory.

Check ES IBANs from code or an AI agent

REST · GET · no key

curl -s 'https://payopskit.com/api/v1/iban/ES9121000418450200051332'

MCP · tools/call · validate_iban

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "validate_iban",
    "arguments": {
      "iban": "ES9121000418450200051332"
    }
  }
}

Response (JSON)

{
  "input": "ES9121000418450200051332",
  "iban": "ES9121000418450200051332",
  "print": "ES91 2100 0418 4502 0005 1332",
  "valid": true,
  "country": {
    "code": "ES",
    "name": "Spain",
    "sepa": true,
    "sepaNote": null
  },
  "checkDigits": "91",
  "expectedCheckDigits": "91",
  "length": {
    "actual": 24,
    "expected": 24
  },
  "bban": "21000418450200051332",
  "bbanFormat": "4!n4!n1!n1!n10!n",
  "bankCode": "2100",
  "branchCode": "0418",
  "parts": [
    {
      "label": "Country code",
      "value": "ES",
      "start": 0,
      "end": 2,
      "kind": "country"
    },
    {
      "label": "Check digits",
      "value": "91",
      "start": 2,
      "end": 4,
      "kind": "check"
    },
    {
      "label": "Bank code",
      "value": "2100",
      "start": 4,
      "end": 8,
      "kind": "bank"
    },
    {
      "label": "Branch code",
      "value": "0418",
      "start": 8,
      "end": 12,
      "kind": "branch"
    },
    {
      "label": "National check digits",
      "value": "45",
      "start": 12,
      "end": 14,
      "kind": "national-check"
    },
    {
      "label": "Account",
      "value": "0200051332",
      "start": 14,
      "end": 24,
      "kind": "account"
    }
  ],
  "checks": {
    "characters": true,
    "country": true,
    "length": true,
    "bbanFormat": true,
    "checksum": true
  },
  "errors": [],
  "notes": [
    "Valid means the structure and check digits are right — not that the account exists or can receive payments.",
    "National check digits inside the BBAN (e.g. the French RIB key, or the Spanish, Belgian and Italian CIN digits) are not verified."
  ]
}

The MCP server is at /mcp (Streamable HTTP, no key); the API and MCP docs show how to connect Claude, Cursor or VS Code.

From a national account number: GET /api/v1/iban/check-digits?country=ES&bban=… or the MCP tool compute_iban_check_digits computes the check digits and the whole IBAN.

Other 24-character IBANs

The same length doesn’t mean the same structure: compare the BBAN formats. All IBAN formats and lengths

Source: the SWIFT IBAN Registry (ISO 13616), transcribed and checked against each country’s registry example; the positions of bank and branch codes are given only where the registry’s are well established. The SWIFT IBAN Registry is the authority. Informational only.