# BR-15 Amount due for payment is required

An invoice shall have the Amount due for payment (BT-115), the outstanding amount the buyer has to pay.

## Problem Description

> **ERROR**: EN 16931 core business rule (CEN)

## Context and Significance

This is an EN 16931 core rule. BT-115 is what the buyer actually pays: BT-112 minus the paid amount (BT-113) plus the rounding amount (BT-114), as checked by BR-CO-16. For a fully prepaid invoice BT-115 is 0.00, but the element must still be present. Because the UBL schema already requires cbc:PayableAmount, BR-15 is mainly reported for CII invoices without ram:DuePayableAmount.

## Solution

Add cac:LegalMonetaryTotal/cbc:PayableAmount equal to BT-112 minus prepaid amount (BT-113) plus rounding amount (BT-114).

- [Validate XML](/en/xrechnung-validator?source=resource&rule=BR-15)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&rule=BR-15)

## Valid Examples

- BT-115 = 1190.00 — nothing prepaid, so the amount due equals the total with VAT (BT-112)

## Invalid Examples

- In CII, ram:SpecifiedTradeSettlementHeaderMonetarySummation has no ram:DuePayableAmount; in UBL a missing cbc:PayableAmount is already an XML schema error

## Code Examples

### Valid XML
```
<ram:SpecifiedTradeSettlementHeaderMonetarySummation>
  <ram:TaxBasisTotalAmount>1000.00</ram:TaxBasisTotalAmount>
  <ram:GrandTotalAmount>1190.00</ram:GrandTotalAmount>
  <ram:DuePayableAmount>1190.00</ram:DuePayableAmount>
</ram:SpecifiedTradeSettlementHeaderMonetarySummation>
```

### Invalid XML
```
<ram:SpecifiedTradeSettlementHeaderMonetarySummation>
  <ram:TaxBasisTotalAmount>1000.00</ram:TaxBasisTotalAmount>
  <ram:GrandTotalAmount>1190.00</ram:GrandTotalAmount>
</ram:SpecifiedTradeSettlementHeaderMonetarySummation>
```

## Affected Fields

- [BT-115 Amount due for payment](/resources/xrechnung/bt-115-amount-due-for-payment)

## Related Rules

- [BR-14](/resources/kosit-validator-errors/br-14-invoice-total-with-vat-required)
- [BR-CO-16](/resources/kosit-validator-errors/br-co-16-amount-due-for-payment-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.