# BR-30 Invoice line period end must not precede its start

If both Invoice line period start date (BT-134) and Invoice line period end date (BT-135) are given, BT-135 shall be later than or equal to BT-134.

## Problem Description

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

## Context and Significance

This is an EN 16931 core rule and the line-level counterpart of BR-29. The invoice line period (BG-26) dates one line, for example a month of rent, a licence term or one billing cycle of a subscription. The error usually comes from swapped start and end dates, a misread date format or a wrong year, often on recurring lines generated from contract data.

## Solution

Correct cac:InvoiceLine/cac:InvoicePeriod (CII: ram:SpecifiedLineTradeSettlement/ram:BillingSpecifiedPeriod) so the end date is on or after the start date, or remove the line period if it is not needed.

- [Validate XML](/en/xrechnung-validator?source=resource&rule=BR-30)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&rule=BR-30)

## Valid Examples

- BT-134 = 2026-02-01, BT-135 = 2026-02-28

## Invalid Examples

- BT-134 = 2026-02-28, BT-135 = 2026-02-01 — end before start

## Code Examples

### Valid XML
```
<cac:InvoiceLine>
  <cac:InvoicePeriod>
    <cbc:StartDate>2026-02-01</cbc:StartDate>
    <cbc:EndDate>2026-02-28</cbc:EndDate>
  </cac:InvoicePeriod>
</cac:InvoiceLine>
```

### Invalid XML
```
<cac:InvoiceLine>
  <cac:InvoicePeriod>
    <cbc:StartDate>2026-02-28</cbc:StartDate>
    <cbc:EndDate>2026-02-01</cbc:EndDate>
  </cac:InvoicePeriod>
</cac:InvoiceLine>
```

## Affected Fields

- [BT-134 Invoice line period start date](/resources/xrechnung/bt-134-invoice-line-period-start-date)
- [BT-135 Invoice line period end date](/resources/xrechnung/bt-135-invoice-line-period-end-date)

## Related Rules

- [BR-29](/resources/kosit-validator-errors/br-29-invoicing-period-end-after-start)

## 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.