# BR-CO-10 Sum of invoice line net amount must equal the total of all line nets

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

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

> **ERROR**: XRechnung 3.0

## Context and Significance

Mismatched line-sum totals are one of the most frequent rejection causes when an ERP exports to XML without rounding alignment. Public-sector portals refuse the file before any human review.

## Solution

Recalculate BT-106 from the actual line nets and write the recomputed value back into the invoice header.

- validate
- convert

## 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

- Lines sum to 175.00 but BT-106 = 174.99 (rounding drift)
- BT-106 left at 0.00 while lines exist

## Technical Details

### Affected Fields
BT-106 Sum of invoice line net amount, 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://erechnungsvalidator.service-bw.de/): Validate your XRechnung files against all BR-DE rules.
- [Convert PDF to XRechnung](/pdf-to-xrechnung): Automatic validation error fixes when converting.

## Related Resources

- [Official Specification](https://xeinkauf.de/xrechnung/)
- [Test Suite](https://github.com/itplr-kosit/xrechnung-testsuite)
- [Complete Error List](/resources/kosit-validator-errors): Overview of all German XRechnung validation rules.