Quaterio
EN 16931 error reference

Conditional field rules

A field became required because of something else you sent. 17 rules.

These are the rules that surprise people, because the field was optional until something else on the invoice made it required.

Send an allowance and you owe a reason for it. Mark a line exempt and you owe an exemption reason. Reference a preceding invoice and you owe its date.

The fix is rarely to remove the trigger. It is to supply the companion field the standard expects alongside it, which usually exists in your source system already.

BR-17
A payee (BG-10) different from the seller was supplied, so the payee name (BT-59) is required. If payment actually goes to the seller, remove the payee group entirely rather than filling it in with the seller again: naming a distinct payee is what tells the buyer to pay someone else.
BR-18
A seller tax representative party (BG-11) was supplied, so its name (BT-62) is required. A representative that cannot be named cannot be verified.
BR-19
A seller tax representative party (BG-11) was supplied, so its postal address (BG-12) is required. The representative is accountable for VAT in their own jurisdiction, which the address establishes.
BR-20
The tax representative address needs a country code (BT-69). It is the field that decides which tax authority the representative answers to, so it is required even when the rest of the address is sparse.
BR-27
The item net price (BT-146) is negative. Prices are always positive; a discount belongs in an allowance (BG-27 on the line, or BG-20 at document level) rather than as a negative price. A credit note is expressed by the document type code (BT-3 = 381), not by negating amounts.
BR-28
The item gross price (BT-148) is negative. As with the net price, use an allowance to reduce it, and a credit note type code to reverse a charge.
BR-29
The invoicing period ends before it starts. BT-74 must be on or after BT-73. Equal dates are allowed, for a single-day period. This is usually a swapped pair, or a period built from a start date plus a negative offset.
BR-30
An invoice line period ends before it starts. BT-135 must be on or after BT-134, and equal dates are allowed.
BR-47
Every VAT breakdown (BG-23) needs its category code (BT-118). The breakdown exists to say how much was taxed at which treatment, so without the code it identifies nothing and cannot be matched to the lines it summarises.
BR-48
Every VAT breakdown needs a rate (BT-119), except where the invoice is not subject to VAT. Note the exemption is narrow: exempt, zero rated and reverse charge categories all still need a rate, and it is 0. Only "not subject to VAT" omits it entirely.
BR-49
A payment instruction (BG-16) was supplied, so it needs a payment means type code (BT-81) saying how payment is expected. Common values are 30 for credit transfer, 58 for SEPA credit transfer and 48 for card.
BR-50
Credit transfer details were supplied, so the account identifier (BT-84) is required. That is the IBAN, or the local account number where IBAN does not apply. Supplying a bank name or BIC alone does not satisfy this: BT-84 is the account being paid into.
BR-51
A full card number must never appear on an invoice. PCI DSS permits at most the first six and last four digits, so send a masked value such as 411111******1111. This is a security rule rather than a formatting one: a compliant invoice is archived and forwarded widely, and a full PAN in it is a breach wherever it lands.
BR-53
A VAT accounting currency (BT-6) was declared, so the total VAT in that currency (BT-111) is required. BT-6 exists for the case where VAT must be reported to the authority in a different currency from the invoice, and stating the currency without the converted amount leaves the reason it was declared unfulfilled.
BR-61
The payment means code says credit transfer (SEPA, local or non-SEPA international), so the account identifier (BT-84) is required. This overlaps BR-50 and is usually the same underlying omission: the payment method was set but the account was never filled in.
BR-B-01
The "Split payment" VAT category (scissione dei pagamenti) only applies to domestic Italian invoices, where the public-sector buyer pays the VAT directly to the tax authority. Both seller and buyer must be Italian. If this is a cross-border invoice, the category is wrong.
BR-B-02
An invoice using the "Split payment" category cannot mix it with other VAT categories. Every line, allowance and charge must be split payment, or none. Issue separate invoices if some items fall under the scheme and others do not.

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