Rule BR-27
The item net price must not be negative
A line's unit price is zero or positive. It is never negative.
Business term BT-146, Item net price. Source: EN 16931. Our wording, not the normative text, which is published in the Peppol BIS Billing 3.0 rule list and was checked against it on 2026-08-16.
Why it fires on invoices that look fine
Almost nobody hits this rule because they forgot the field exists. They hit it because something between their system and the document dropped it, changed its shape, or filled it with a value that is right somewhere else. These are the causes worth checking first.
- A credit or a return was expressed by negating the price, which is the intuitive move and the wrong one.
- A discount was applied by subtracting it from the price and the result went below zero.
What to change
- Express a return with a negative quantity and a positive price. That is the modelled way to do it and it keeps the price meaning what it says.
- Or issue a credit note, which is a separate document type and is usually what the buyer's system expects.
- Put discounts in the allowance fields rather than folding them into the price, so the document still shows what was actually charged per unit.
The validator runs in your browser. Nothing is uploaded, and you can confirm that yourself with the network panel open.
Rules you are likely to hit next
A document that breaks BR-27 usually breaks one of these too, because the same mapping gap tends to affect neighbouring fields.
Questions people actually ask
- What does BR-27 mean?
- A line's unit price is zero or positive. It is never negative.
- Which field does BR-27 apply to?
- BT-146, Item net price. That is the name the semantic model uses, which is what you search for in your own system's mapping when the identifier alone does not tell you which field to look at.
- Does our validator check BR-27?
- Yes. Paste your invoice data into the free validator and it reports this rule with the value it actually saw, without the document leaving your browser.