# BR-CO-10 Sum of invoice line net amounts (BT-106) must equal the sum of all line net amounts (BT-131)

The document-level Sum of invoice line net amounts (BT-106) must equal the arithmetic sum of every Invoice line net amount (BT-131).

## Problem Description

> **ERROR**: EN 16931 calculation and consistency rule (BR-CO)

> **Where BR-CO-10 is checked**
>
> A validator checks an e-invoice in stages. First the file must be well-formed XML that matches the UBL or CII schema (XSD). Then the EN 16931 business rules run: BR core rules, BR-CO calculations, BR-CL code lists, BR-DEC decimals and VAT-category rules such as BR-S. Next come the national or network rules that BT-24 selects: BR-DE for XRechnung, PEPPOL-EN16931 for Peppol BIS Billing. The report lists every failed rule: one error means reject, warnings alone still mean accept. BR-CO-10: EN 16931 calculation rule, reported in the stage “EN 16931 rules”.

## Context and Significance

The validator adds up all BT-131 values and compares the result with BT-106 exactly, without tolerance. A difference usually comes from rounding: the ERP calculates the total from unrounded quantity × price values, while each line amount in the XML is rounded to two decimals. Another cause is a line that was deleted or added after the totals were calculated.

## Solution

Round each invoice line net amount (BT-131) to two decimals first, then write their exact sum into BT-106 in the totals block (UBL: cac:LegalMonetaryTotal/cbc:LineExtensionAmount; CII: ram:SpecifiedTradeSettlementHeaderMonetarySummation/ram:LineTotalAmount).

- [Validate XML](/en/xrechnung-validator?source=resource&rule=BR-CO-10)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&rule=BR-CO-10)

## Valid Examples

- Lines 100.00 + 50.00 + 25.00 yield BT-106 = 175.00
- Single line of 99.99 yields BT-106 = 99.99

## Invalid Examples

- Three lines of 10.005 are each rounded to 10.01 (sum 30.03), but BT-106 = 30.02 was calculated from the unrounded sum 30.015
- BT-106 left at 0.00 while lines exist

## Affected Fields

- [BT-106 Sum of invoice line net amount](/resources/xrechnung/bt-106-sum-of-invoice-line-net-amount)
- [BT-131 Invoice line net amount](/resources/xrechnung/bt-131-invoice-line-net-amount)

## Related Rules

- [BR-CO-13](/resources/kosit-validator-errors/br-co-13-invoice-total-without-vat-must-match-totals-chain)
- [BR-CO-11](/resources/kosit-validator-errors/br-co-11-sum-of-document-allowances-must-match)

## Validation Tools

- [Official KoSIT Validator](https://github.com/itplr-kosit/validator): Run the official KoSIT validator with the XRechnung configuration to check EN 16931 and XRechnung rules.
- [Convert PDF to XRechnung](/pdf-to-xrechnung): Find validation errors during conversion and review each correction.

## Related Resources

- [Official Specification](https://docs.peppol.eu/poacc/billing/3.0/rules/ubl-tc434/)
- [Test Suite](https://github.com/itplr-kosit/xrechnung-testsuite)
- [All validation errors](/resources/kosit-validator-errors): Overview of the EN 16931, XRechnung and Peppol validation rules explained here.