# BR-CO-20

> If Invoice line period (BG-26) is used, the Invoice line period start date (BT-134) or the Invoice line period end date (BT-135) shall be filled, or both.

Checked against Peppol BIS Billing 3.0 2026.5

Canonical: https://einvoicecheck.eu/rules/br-co-20

## Official rule text

If Invoice line period (BG-26) is used, the Invoice line period start date (BT-134) or the Invoice line period end date (BT-135) shall be filled, or both.

## Why did my invoice fail BR-CO-20?

If an Invoice line period (BG-26) is used, the Invoice line period start date (BT-134) or end date (BT-135) must be present (one or both). As with the document-level period, a line-level period group must carry at least one date to be meaningful.

## Common causes

- cac:InvoiceLine/cac:InvoicePeriod present but StartDate and EndDate both missing.
- Line period wrapper always generated even when the line has no service period.
- Only one date intended but the wrong (empty) element rendered.
- Period set at document level but an empty duplicate emitted on the line.

## How do I fix it?

```
On the line, set at least one date: <cac:InvoicePeriod><cbc:StartDate>2026-06-01</cbc:StartDate></cac:InvoicePeriod>, or remove the line-level InvoicePeriod if not applicable.
```