# BR-O-08 Not-subject-to-VAT taxable amount must equal its line and adjustment sum

In a VAT breakdown (BG-23) where the VAT category code (BT-118) is "Not subject to VAT" (O), the VAT category taxable amount (BT-116) shall equal the sum of invoice line net amounts (BT-131) minus the sum of document level allowance amounts (BT-92) plus the sum of document level charge amounts (BT-99) that carry category O.

## Problem Description

> **ERROR**: EN 16931 VAT category rule

## Context and Significance

This EN16931 rule keeps the amount of the O breakdown consistent with the category O lines, allowances and charges, so the summary can be checked. In practice, the gap appears when a document level allowance or charge with category O is left out of BT-116.

## Solution

Compute BT-116 as Σ BT-131 − Σ BT-92 + Σ BT-99 restricted to the category-O lines, allowances and charges, and write it into the O TaxSubtotal TaxableAmount.

- [Validate XML](/en/xrechnung-validator?source=resource&rule=BR-O-08)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&rule=BR-O-08)

## Valid Examples

- O lines net 100.00, no O allowances or charges → BT-116 = 100.00

## Invalid Examples

- O lines net 100.00 but BT-116 reported as 90.00

## Code Examples

### Valid XML
```
<cac:TaxSubtotal>
  <cbc:TaxableAmount currencyID="EUR">100.00</cbc:TaxableAmount>
  <cbc:TaxAmount currencyID="EUR">0.00</cbc:TaxAmount>
  <cac:TaxCategory><cbc:ID>O</cbc:ID><cac:TaxScheme><cbc:ID>VAT</cbc:ID></cac:TaxScheme></cac:TaxCategory>
</cac:TaxSubtotal>
```

### Invalid XML
```
<cac:TaxSubtotal>
  <cbc:TaxableAmount currencyID="EUR">90.00</cbc:TaxableAmount>
  <cbc:TaxAmount currencyID="EUR">0.00</cbc:TaxAmount>
  <cac:TaxCategory><cbc:ID>O</cbc:ID><cac:TaxScheme><cbc:ID>VAT</cbc:ID></cac:TaxScheme></cac:TaxCategory>
</cac:TaxSubtotal>
```

## Affected Fields

- [BT-116 VAT category taxable amount](/resources/xrechnung/bt-116-vat-category-taxable-amount)
- [BT-131 Invoice line net amount](/resources/xrechnung/bt-131-invoice-line-net-amount)
- [BT-92 Document level allowance amount](/resources/xrechnung/bt-92-document-level-allowance-amount)
- [BT-99 Document level charge amount](/resources/xrechnung/bt-99-document-level-charge-amount)

## Related Rules

- [BR-O-01](/resources/kosit-validator-errors/br-o-01-not-subject-vat-breakdown-required)
- [BR-O-09](/resources/kosit-validator-errors/br-o-09-not-subject-tax-amount-zero)
- [BR-CO-18](/resources/kosit-validator-errors/br-co-18-vat-breakdown-required)

## 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.