Does BR-CO-15 always mean the VAT calculation is wrong?

No. It means total including VAT does not equal total excluding VAT plus total VAT. Any of those values may be inconsistent.

Can a one-cent difference cause rejection?

Yes. A small difference can fail a calculation rule. Check the specific rule rather than assuming a one-cent difference is always tolerated.

Can I change only the grand total?

Usually not. Recalculate from the first incorrect line, allowance, charge or VAT breakdown so all dependent totals agree.

Invoice totals don’t match: fix calculations and rounding

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Peppol checks that line amounts, VAT breakdowns and invoice totals agree with the EN 16931 calculation chain. A common cause of mismatches is calculating and rounding VAT on every line, then summing it instead of calculating VAT on each category-and-rate taxable amount.

Rebuild the totals in order

Start with each line: quantity multiplied by the net price per price base quantity, minus line allowances and plus line charges. Then add the line net amounts. If the price is quoted per 100 units, account for that base quantity rather than multiplying by the displayed price alone.

Sum line net amounts: BR-CO-10.
Subtract document allowances and add document charges: total excluding VAT, checked by BR-CO-13.
Calculate VAT for each category-and-rate taxable amount; round each VAT amount to two decimals.
Sum VAT breakdown amounts: BR-CO-14.
Add total VAT to the total excluding VAT: total including VAT, checked by BR-CO-15.
Subtract prepaid amounts and add any payable rounding amount: amount due, checked by BR-CO-16.

Round VAT at breakdown level

Group taxable amounts by VAT category and rate, including the relevant document allowances and charges. Calculate VAT on each group and round that VAT amount to two decimals. Do not replace this calculation with a sum of individually rounded line VAT amounts.

For example, two standard-rated lines of 0.03 at 21% give a taxable amount of 0.06 and VAT of 0.01. Rounding VAT separately on each line gives 0.01 plus 0.01, producing a different result.

Fix the first inconsistent amount

Use the free XML validator on this site to identify the failed calculation rule. BR-S-08 checks the standard-rated taxable base, while R120 checks line net calculations. Fix the first incorrect value in your accounting software, then regenerate and validate the XML.

Do not hide a VAT mismatch in a payable rounding amount: that field adjusts the amount due, not the VAT breakdown. Also check that the XML and the displayed invoice use the same source amounts.

Frequently asked questions

Does BR-CO-15 always mean the VAT calculation is wrong?: No. It means total including VAT does not equal total excluding VAT plus total VAT. Any of those values may be inconsistent.
Can a one-cent difference cause rejection?: Yes. A small difference can fail a calculation rule. Check the specific rule rather than assuming a one-cent difference is always tolerated.
Can I change only the grand total?: Usually not. Recalculate from the first incorrect line, allowance, charge or VAT breakdown so all dependent totals agree.