BR-CO-15 and the Other Reasons Invoice Totals Do Not Match

ARLing s. r. o. · 11 September 2026

Two Kinds of Rules Inside EN 16931

EN 16931 does not treat invoice totals as a separate feature bolted onto the rest of the format. Its schematron splits the whole rule set into two different jobs. The plain BR rules are numbered BR-01 to BR-65, though only 58 of them actually exist, and they check that a required piece of data is present at all, in the right place and in the right format. BR-02 is a plain example of this first group: an invoice must have an invoice number, and a file that leaves it out is rejected outright, with no arithmetic involved.

The BR-CO rules are a separate, smaller family, numbered BR-CO-01 to BR-CO-26 though only 24 of them actually exist, and they check something different: that two or more amounts calculated from other figures on the same invoice actually agree with each other. BR-CO-15 and BR-CO-10 both live in this second group, which is why a missing invoice number and a wrong total feel like different kinds of mistakes even though the same schematron run reports both of them.

What BR-CO-15 Actually Compares

The normative text of the rule reads: Invoice total amount with VAT (BT-112) = Invoice total amount without VAT (BT-109) + Invoice total VAT amount (BT-110). In plain terms, whatever the invoice states as its grand total including tax has to equal the net total plus the tax total exactly, with nothing left over and nothing missing.

BT-112, BT-109 and BT-110 are three separate fields on the invoice, and the rule requires the first to equal the sum of the other two exactly, not approximately. That means all three have to be kept consistent with each other every time one of them changes.

BR-CO-10: When the Mismatch Starts at the Line Level

BR-CO-15 checks the very last step of the sum, where net plus tax has to equal gross. An invoice can already be broken before it gets that far, and BR-CO-10 is what catches the earlier failure. Its text reads: Sum of Invoice line net amount (BT-106) = Σ Invoice line net amount (BT-131). In other words, adding up the net amount of every individual line on the invoice has to produce the same net total that the header of the invoice states separately.

The two rules check related but distinct amounts on the invoice. BR-CO-10 checks whether the invoice lines add up to the line-sum field in the header, while BR-CO-15 checks a separate pair of totals further along the same calculation. Checking the line-level sum first is therefore a more direct way to find the source of a totals error than adjusting the final total on its own.

VAT Categories and Allowances Add Their Own Arithmetic

Totals problems are not only about BR-CO-15 and BR-CO-10. The VAT category code on each invoice line, taken from UNTDID 5305, decides which extra rule group applies to that line: S for the standard rate, Z for zero rated, E for exempt, AE for reverse charge, K for an intra community supply, G for export outside the European Union, O for not subject to VAT, and further codes for the Canary Islands and for Ceuta and Melilla. Categories S, Z, E, AE and G each carry ten rules of their own, O carries fourteen, and K carries twelve, so the wrong category code does not just mislabel a line, it switches on an entirely different block of arithmetic checks.

Discounts and surcharges bring a rule of their own on top of that. Under Peppol BIS Billing 3.0, rule PEPPOL-EN16931-R040 states that an allowance or charge amount must equal the base amount multiplied by the percentage and divided by 100, whenever both a base amount and a percentage are given on the invoice. A discount typed in as a rounded amount instead of the exact product of its own base and percentage will fail this rule even when every other total on the invoice is correct.

Frequently asked questions

Conclusion

BR-CO-15 is one line inside a much larger rule set that also includes BR-CO-10, the VAT category rule groups, and the allowance and charge rule, so a rejection is worth checking against all of them rather than assuming BR-CO-15 alone is at fault. Working out which of these related rules actually triggered the rejection is a faster way to fix the file than adjusting the final total by trial and error. For more on preparing invoices that meet the EN 16931 standard, see ARLing's e-invoicing page.