# BR-AE-08 Reverse charge taxable amount must equal the reverse charge net sum

In a VAT breakdown (BG-23) where the VAT category code (BT-118) is "Reverse charge" (AE), the VAT category taxable amount (BT-116) shall equal the sum of invoice line net amounts (BT-131) minus document level allowance amounts (BT-92) plus document level charge amounts (BT-99) whose VAT category codes (BT-151, BT-95, BT-102) are "Reverse charge".

## Problem Description

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

## Context and Significance

This EN16931 rule reconciles the reverse charge taxable base with the underlying lines and adjustments so the shifted VAT liability is reported on a correct basis. In practice, the error occurs when a document level allowance or charge coded AE is left out of the AE taxable amount.

## Solution

Recompute BT-116 for the AE breakdown as Σ BT-131 − Σ BT-92 + Σ BT-99 over the reverse charge elements, then write that value into the AE cac:TaxSubtotal/cbc:TaxableAmount.

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

## Valid Examples

- AE lines Σ BT-131 = 1000.00, no AE allowances/charges, BT-116 = 1000.00

## Invalid Examples

- AE lines Σ BT-131 = 1000.00 but BT-116 = 900.00 in the AE breakdown

## Code Examples

### Valid XML
```
<cac:TaxSubtotal>
  <cbc:TaxableAmount currencyID="EUR">1000.00</cbc:TaxableAmount>
  <cbc:TaxAmount currencyID="EUR">0.00</cbc:TaxAmount>
  <cac:TaxCategory>
    <cbc:ID>AE</cbc:ID>
    <cbc:Percent>0</cbc:Percent>
    <cac:TaxScheme><cbc:ID>VAT</cbc:ID></cac:TaxScheme>
  </cac:TaxCategory>
</cac:TaxSubtotal>
```

### Invalid XML
```
<cac:TaxSubtotal>
  <cbc:TaxableAmount currencyID="EUR">900.00</cbc:TaxableAmount>
  <cbc:TaxAmount currencyID="EUR">0.00</cbc:TaxAmount>
  <cac:TaxCategory>
    <cbc:ID>AE</cbc:ID>
    <cbc:Percent>0</cbc:Percent>
    <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)
- [BT-118 VAT category code](/resources/xrechnung/bt-118-vat-category-code)

## Related Rules

- [BR-AE-01](/resources/kosit-validator-errors/br-ae-01-reverse-charge-vat-breakdown-required)
- [BR-AE-09](/resources/kosit-validator-errors/br-ae-09-reverse-charge-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.