# PEPPOL-EN16931-R110

> Start date of line period MUST be within invoice period.

Checked against Peppol BIS Billing 3.0 2026.5

Canonical: https://einvoicecheck.eu/rules/peppol-en16931-r110

## Official rule text

Start date of line period MUST be within invoice period.

## Why did my invoice fail PEPPOL-EN16931-R110?

The start date of an invoice line's billing period (BT-134) must fall within the document-level invoicing period (BT-73 to BT-74). A line period cannot begin before the invoice period starts or after it ends, since line periods must be contained by the overall period they detail.

## Common causes

- A line InvoicePeriod/StartDate is earlier than the header InvoicePeriod/StartDate.
- A line period start falls after the header period EndDate due to a date typo or timezone shift.
- The header invoice period was set narrower than one of the individual line periods.

## How do I fix it?

```
Ensure the line start is inside the header window, e.g. header 2026-01-01 to 2026-01-31 and line <cac:InvoicePeriod><cbc:StartDate>2026-01-10</cbc:StartDate></cac:InvoicePeriod>.
```