Iban compute from bban

iban-compute-from-bban · version 1.0.0 · Identifiers & check digits · free, no key needed

Compute the MOD 97-10 check digits and full IBAN for a country code and BBAN, using the pinned IBAN registry.

Use when you need to: build an iban from a bban · compute iban check digits from account number · generate an iban for this domestic bank account.

Decide before calling

Read the versioned contract and the supported scope below. Reuse iban-compute-from-bban@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use iban-compute-from-bban@1.0.0 for build an iban from a bban. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• build an iban from a bban
• compute iban check digits from account number
• generate an iban for this domestic bank account
• convert a local bank account and sort code to an iban
• create a swift-ready iban from bank and branch codes
• חישוב ספרות ביקורת מחשבון בנק מקומי

Not supported

• validating a full IBAN that may already be wrong (use iban-validate)
• countries not in the pinned IBAN registry
• case-folding or space-stripping the input (country and bban must already be normalized)

Behavior

• country and bban are taken exactly as given; this tool does not case-fold or strip spaces. country must already match ^[A-Z]{2}$ and bban must already match ^[A-Z0-9]+$, 1-30 characters, or the call throws invalid_input.
• spec = the pinned IBAN registry entry for country (getIbanSpec, the same table iban-validate uses). If spec is null, throw unsupported_input with details {country}.
• If bban does not match the registry BBAN notation for country (bbanMatches, which also enforces the exact expected length spec.length - 4), throw invalid_input with details {reason: 'bban_format'}.
• MOD 97-10 check: rearranged = bban + country + '00'. digits = alnum_to_digits(rearranged). r = digits mod 97. check_digits = 98 - r (range 02-98; r = 0 gives '98', never '00'), zero-padded to 2 decimal digits.
• iban = country + check_digits + bban (electronic form, no spaces). print = iban split into groups of 4 characters joined by a single space. data_version is the same pinned IBAN registry version iban-validate reports.

Input

• country (string, required): pattern ^[A-Z]{2}$
• bban (string, required): min length 1; max length 30; pattern ^[A-Z0-9]+$

Output

• iban (string, required): min length 5; max length 34
• check_digits (string, required): pattern ^[0-9]{2}$
• print (string, required): min length 5; max length 42
• data_version (string, required)

Limits

• max bban bytes: 30

Example

Request input:

{
  "country": "GB",
  "bban": "NWBK60161331926819"
}

Response:

{
  "result": {
    "iban": "GB29NWBK60161331926819",
    "check_digits": "29",
    "print": "GB29 NWBK 6016 1331 9268 19",
    "data_version": "swift-iban-registry-103-2026-09.subset-80"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "iban-compute-from-bban",
  "version": "1.0.0",
  "input": {
    "country": "GB",
    "bban": "NWBK60161331926819"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/iban-compute-from-bban/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"country":"GB","bban":"NWBK60161331926819"}'

The machine-readable contract is at /v1/tools/iban-compute-from-bban/versions/1.0.0.

CLI

node cli.mjs run iban-compute-from-bban 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

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• Bic validate: Validate a Business Identifier Code's ISO 9362:2022 structure and parse its party prefix, country, location and branch.
• Isin validate: Validate a 12-character ISIN's ISO 6166 Luhn check digit and parse its country prefix, NSIN and NSIN scheme.
• Iccid validate: Validate a 19/20-digit ICCID's Luhn check digit, require the 89 major industry id, split issuer/account digits.