# BR-CO-17 VAT category tax amount must equal taxable amount times rate divided by 100

VAT category tax amount (BT-117) must equal VAT category taxable amount (BT-116) multiplied by VAT category rate (BT-119) divided by 100, rounded to two decimals.

## Problem Description

VAT category tax amount (BT-117) must equal VAT category taxable amount (BT-116) multiplied by VAT category rate (BT-119) divided by 100, rounded to two decimals.

> **ERROR**: XRechnung 3.0

## Context and Significance

This rule is checked once per VAT breakdown line. Half-up versus banker’s rounding mismatches between the source ERP and the converter are the typical cause of failure.

## Solution

Recompute every BT-117 as round(BT-116 × BT-119 / 100, 2) using the rounding mode the receiver expects (commercial rounding for German receivers).

- validate
- convert

## Valid Examples

- BT-116 = 100.00, BT-119 = 19 → BT-117 = 19.00
- BT-116 = 84.03, BT-119 = 19 → BT-117 = 15.97

## Invalid Examples

- BT-116 = 100.00, BT-119 = 19 but BT-117 = 19.01
- BT-117 left at 0.00 with non-zero BT-116 and BT-119

## Technical Details

### Affected Fields
BT-117 VAT category tax amount, BT-116 VAT category taxable amount, BT-119 VAT category rate

## Related Rules

- [BR-CO-14](/resources/kosit-validator-errors/br-co-14-invoice-total-vat-must-equal-sum-of-vat-categories)
- [BR-S-5](/resources/kosit-validator-errors/br-s-5-standard-rated-vat-breakdown-rate-must-be-positive)
- [BR-S-8](/resources/kosit-validator-errors/br-s-8-standard-rated-taxable-amount-must-match-line-and-allowance-sum)

## 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.