IBAN format · LU

Luxembourg IBAN format: 20 characters.

Luxembourg IBANs have 20 characters: the country code LU, two check digits and a 16-character BBAN, the national account number, laid out as 3!n13!c.

Luxembourg IBAN structure

LU280019400644750000

Country code: LU
Check digits: 28
Bank code: 001
Account: 9400644750000

Parts of a Luxembourg IBAN and their positions
Positions	Part	In the example
1–2	Country code	LU
3–4	Check digits	28
5–7	Bank code	001
8–20	Account	9400644750000

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. 3!n13!c reads:

The Luxembourg BBAN format, segment by segment
Positions	Notation	Holds	Example
5–7	3!n	3 digitsBank code	001
8–20	13!c	13 letters or digits	9400644750000

Luxembourg IBAN example

LU28 0019 4006 4475 0000 is the sample the SWIFT IBAN Registry publishes for Luxembourg: a well-formed IBAN for showing the format, not a real account. Written electronically it has no spaces (LU280019400644750000); 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
0019400644750000LU28
Replace each letter with two digits (A = 10 … Z = 35)
L = 21, U = 30
0019400644750000213028
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 (LU00…), repeat steps 1–3: remainder 70. The check digits are 98 − 70 = 28.

SEPA

Luxembourg is in the Single Euro Payments Area, so SEPA credit transfers and direct debits can reach LU 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 LU IBANs from code or an AI agent

REST · GET · no key

curl -s 'https://payopskit.com/api/v1/iban/LU280019400644750000'

MCP · tools/call · validate_iban

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "validate_iban",
    "arguments": {
      "iban": "LU280019400644750000"
    }
  }
}

Response (JSON)

{
  "input": "LU280019400644750000",
  "iban": "LU280019400644750000",
  "print": "LU28 0019 4006 4475 0000",
  "valid": true,
  "country": {
    "code": "LU",
    "name": "Luxembourg",
    "sepa": true,
    "sepaNote": null
  },
  "checkDigits": "28",
  "expectedCheckDigits": "28",
  "length": {
    "actual": 20,
    "expected": 20
  },
  "bban": "0019400644750000",
  "bbanFormat": "3!n13!c",
  "bankCode": "001",
  "branchCode": null,
  "parts": [
    {
      "label": "Country code",
      "value": "LU",
      "start": 0,
      "end": 2,
      "kind": "country"
    },
    {
      "label": "Check digits",
      "value": "28",
      "start": 2,
      "end": 4,
      "kind": "check"
    },
    {
      "label": "Bank code",
      "value": "001",
      "start": 4,
      "end": 7,
      "kind": "bank"
    },
    {
      "label": "Account",
      "value": "9400644750000",
      "start": 7,
      "end": 20,
      "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=LU&bban=… or the MCP tool compute_iban_check_digits computes the check digits and the whole IBAN.

Other 20-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.