Negative invoice lines

Where negative lines come from

Three cases come up again and again in practice. First, a correction within the same invoice: an item was entered twice or billed incorrectly and is reversed right below, instead of issuing a separate corrective invoice. Second, deposits and returns: returnable packaging or returned goods are offset against the next delivery — the return appears as its own line with a negative amount next to the new items. Third, offsetting prepayments: the final invoice lists all supplies and deducts previously invoiced down payments as negative lines.

The third case deserves a closer look: for amounts already paid, EN 16931 also provides the field BT-113 (prepaid amount), which per BR-CO-16 is deducted from the gross total after VAT. A negative line, by contrast, acts before VAT and reduces the taxable amount. Which route is correct depends on whether the prepayment invoice already charged VAT — a tax question, not a technical one. Both routes are conformant.

What the standard allows — and what it doesn’t

The line net amount BT-131 may be negative. The clean way to build it is: negative quantity, positive price. The invoiced quantity BT-129 is explicitly signed — taking back one unit is simply -1. The item net price BT-146, however, must not be negative: that is exactly what business rule BR-27 of EN 16931 says. Billhorse does not check BR-27 yet — but receiving systems and other validators (such as the KOSIT tool) do, and an invoice with a negative price gets rejected there. So never negate the price; always negate the quantity.

A negative line in UBL and CII

In UBL, a return looks like this — negative quantity, positive price, with LineExtensionAmount following as quantity × price:

<cac:InvoiceLine>
  <cbc:ID>2</cbc:ID>
  <cbc:InvoicedQuantity unitCode="C62">-1</cbc:InvoicedQuantity>
  <cbc:LineExtensionAmount currencyID="EUR">-89.00</cbc:LineExtensionAmount>
  <cac:Item>
    <cbc:Name>Return: charger</cbc:Name>
    <cac:ClassifiedTaxCategory>
      <cbc:ID>S</cbc:ID>
      <cbc:Percent>19</cbc:Percent>
      <cac:TaxScheme><cbc:ID>VAT</cbc:ID></cac:TaxScheme>
    </cac:ClassifiedTaxCategory>
  </cac:Item>
  <cac:Price>
    <cbc:PriceAmount currencyID="EUR">89.00</cbc:PriceAmount>
  </cac:Price>
</cac:InvoiceLine>

The same in CII (ZUGFeRD/Factur-X): the quantity sits in the delivery part as BilledQuantity, the price as ChargeAmount inside NetPriceProductTradePrice, and the line amount as LineTotalAmount in the line monetary summation:

<ram:IncludedSupplyChainTradeLineItem>
  <ram:AssociatedDocumentLineDocument>
    <ram:LineID>2</ram:LineID>
  </ram:AssociatedDocumentLineDocument>
  <ram:SpecifiedTradeProduct>
    <ram:Name>Return: charger</ram:Name>
  </ram:SpecifiedTradeProduct>
  <ram:SpecifiedLineTradeAgreement>
    <ram:NetPriceProductTradePrice>
      <ram:ChargeAmount>89.00</ram:ChargeAmount>
    </ram:NetPriceProductTradePrice>
  </ram:SpecifiedLineTradeAgreement>
  <ram:SpecifiedLineTradeDelivery>
    <ram:BilledQuantity unitCode="C62">-1</ram:BilledQuantity>
  </ram:SpecifiedLineTradeDelivery>
  <ram:SpecifiedLineTradeSettlement>
    <ram:ApplicableTradeTax>
      <ram:TypeCode>VAT</ram:TypeCode>
      <ram:CategoryCode>S</ram:CategoryCode>
      <ram:RateApplicablePercent>19</ram:RateApplicablePercent>
    </ram:ApplicableTradeTax>
    <ram:SpecifiedTradeSettlementLineMonetarySummation>
      <ram:LineTotalAmount>-89.00</ram:LineTotalAmount>
    </ram:SpecifiedTradeSettlementLineMonetarySummation>
  </ram:SpecifiedLineTradeSettlement>
</ram:IncludedSupplyChainTradeLineItem>

Allowance or negative line?

Not every deduction belongs in its own line. A discount on one item — volume discount, promotional price — is a line-level allowance (BG-27) with its amount in BT-136; it stays part of the same line and reduces that line’s BT-131. A discount on the whole invoice — loyalty rebate, agreed general reduction — is a document-level allowance (BG-20, amount in BT-92) and feeds into the allowance total BT-107. A negative line is the right tool when you are modelling a transaction of its own, with its own quantity and its own item: a return, a deposit refund, an offset prepayment. Rule of thumb: if the deduction refers to a delivery of something, it is a line; if it is merely a pricing component, it is an allowance.

The totals still have to add up

Negative lines change nothing about the standard’s arithmetic — they are simply included in the sums. BR-CO-10 requires the sum of line amounts BT-106 to equal the sum of all line net amounts (BT-131) exactly, negative values included. The chain builds on top of that: per BR-CO-13, the net total BT-109 = BT-106 − allowances (BT-107) + charges (BT-108), and per BR-CO-15, the gross total BT-112 = BT-109 + VAT (BT-110). Always compute these fields from the lines instead of maintaining them separately. If the sum of lines turns negative overall, that is formally permitted — but in most cases a credit note (type code 381) is the more appropriate document.

VAT: the category has to match

A negative line carries the same VAT category and the same rate as the supply it corrects — the return of an item billed at 19% goes into category S at 19%, not into Z or E. The taxable amount of each category is the sum of its line amounts, so the negative line reduces the base of its category. Put it in the wrong one and the VAT breakdown (BG-23) and the rules of the BR-S family fall apart — up to contradictions like an exemption reason inside a taxed category (BR-S-10), and the VAT total no longer satisfies BR-CO-14.

To see whether your invoice with negative lines passes, run it through the browser validator — the file never leaves your machine. To integrate the same engine into your own software, there is the developer API (private beta) with the validate and parse endpoints.

← All guides · Last updated: 2026-07-04