# BR-CO-19 Invoicing period needs a start or end date

If the invoicing period (BG-14) is used, the invoicing period start date (BT-73) or the invoicing period end date (BT-74) shall be filled, or both.

## Problem Description

> **ERROR**: EN 16931 calculation and consistency rule (BR-CO)

## Context and Significance

This EN 16931 rule forbids an empty invoicing period without any date. The error typically occurs when the ERP always generates the period element, even when no service or billing dates are known for the invoice.

## Solution

When an invoicing period (BG-14) is present, provide at least its start date (BT-73) or end date (BT-74); otherwise remove the empty element. UBL: cac:InvoicePeriod/cbc:StartDate or cbc:EndDate; a cac:InvoicePeriod that contains only cbc:DescriptionCode (the VAT point date code, BT-8) is accepted. CII: ram:BillingSpecifiedPeriod/ram:StartDateTime or ram:EndDateTime.

- [Validate XML](/en/xrechnung-validator?source=resource&rule=BR-CO-19)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&rule=BR-CO-19)

## Valid Examples

- BT-73 = 2026-01-01 with BT-74 = 2026-01-31
- UBL: cac:InvoicePeriod containing only cbc:DescriptionCode = 3 (BT-8)

## Invalid Examples

- cac:InvoicePeriod present without BT-73 and BT-74 (and, in UBL, without cbc:DescriptionCode)

## Code Examples

### Valid XML
```
<cac:InvoicePeriod>
  <cbc:StartDate>2026-01-01</cbc:StartDate>
  <cbc:EndDate>2026-01-31</cbc:EndDate>
</cac:InvoicePeriod>
```

### Invalid XML
```
<cac:InvoicePeriod>
</cac:InvoicePeriod>
```

## Affected Fields

- [BG-14 Invoicing period](/resources/xrechnung/bt-73-invoicing-period-start-date)
- [BT-73 Invoicing period start date](/resources/xrechnung/bt-73-invoicing-period-start-date)
- [BT-74 Invoicing period end date](/resources/xrechnung/bt-74-invoicing-period-end-date)

## Related Rules

- [BR-CO-20](/resources/kosit-validator-errors/br-co-20-line-period-date-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.