Attestwire › Rule reference › BR-05

BR-05 An invoice must have a currency code

noun · EN 16931 · fatal · BT-5

an amount with no currency is just a number.

Your invoice was refused because it does not say which currency its amounts are in. Every invoice needs a three-letter currency code such as EUR, and this is a one-field fix. In the standard the currency code is field 5, written BT-5, and BR-05 is the rule that checks it.

Business term

BT-5 — Invoice currency code

Severity

fatal

Applies to

All profiles

The fix

Put the currency code on the invoice, currency: "EUR". Store the currency alongside the amounts, on the same record, and never derive it at render time from the customer’s country. If your product only ever bills in euros today, hard-code "EUR" at the point where you build the invoice rather than leaving the field to a default somewhere further in; a default you cannot see is the one that changes when someone adds a second currency next year.

If VAT has to be reported in a different currency from the invoice, that is BT-6, a separate field, not a second value in this one.

What the rule requires

The invoice needs a currency, given as the three-letter code from the ISO 4217 list: EUR, SEK, CHF. Uppercase. The code, never the symbol: € is not a value this field accepts, and neither is the numeric ISO 4217 code. This is business term BT-5.

One code covers the whole document. EN 16931 has no per-line currency, so an invoice that mixes currencies cannot be expressed here; it is two invoices.

Our input check fires when currency is missing, empty or only whitespace.

An Invoice shall have an Invoice currency code (BT-5).

Failing and passing

validateInput({
  profile: "en16931",
  invoiceNumber: "2026-000142",
  issueDate: "2026-08-09",
  // currency omitted         <- BR-05
  seller: { /* ... */ },
  buyer:  { /* ... */ },
  lines:  [ /* ... */ ],
});
// -> { valid: false, errors: [ { rule: "BR-05", ... } ] }

validateInput({
  profile: "en16931",
  invoiceNumber: "2026-000142",
  issueDate: "2026-08-09",
  currency: "EUR",           // uppercase ISO 4217 alphabetic code
  seller: { /* ... */ },
  buyer:  { /* ... */ },
  lines:  [ /* ... */ ],
});
// -> { valid: true, errors: [] }

Why it exists

Every monetary amount on the invoice is a bare number. The currency code is the only thing that says what those numbers mean, and a receiving system has no way to guess it from the seller’s country, the buyer’s, or the amounts themselves. A German seller invoicing a Swedish buyer in Swedish kronor is ordinary. Without the code, the amounts cannot be booked.

What the library returns

The full error returned by @attestwire/en16931. It includes the rule ID, affected field and suggested correction. Developers can use this object in their application:

{
  "rule": "BR-05",
  "field": "BT-5",
  "severity": "fatal",
  "message": "An invoice must have a currency code (BT-5) from ISO 4217, but none was provided. Every monetary amount in the document is interpreted against this code.",
  "fix": "Set currency to the three-letter ISO 4217 alphabetic code, e.g. \"EUR\". Use the code, not the symbol.",
  "example": "\"currency\": \"EUR\"",
  "xpath": "/ubl:Invoice/cbc:DocumentCurrencyCode",
  "docsUrl": "https://attestwire.com/rules/BR-05"
}

xpath is always a UBL path. On a CII invoice, look for the matching CII field instead.

How our check differs

See also: BR-CL-03 — the currency code must be on the ISO 4217 list; BR-CL-04 — the same question, asked of the VAT accounting currency.