# UBL-SR-36

Quoted from a public specification. This page is not a validator, and it is not tax, legal, or accounting advice.

- Country: EU
- Syntax: UBL
- Severity: fatal
- Statement language: en
- Last verified: 2026-10-18

## Official statement

> Invoice line period shall occur maximum once

Source: https://docs.peppol.eu/poacc/billing/3.0/rules/ubl-tc434/UBL-SR-36/

Peppol BIS Billing 3.0, May 2026 release, EN 16931 model bound to UBL

Severity note: fatal, from the Flag column of the Peppol BIS Billing 3.0 UBL rules index retrieved 2026-10-18.

## Plain-language reading

The invoice line period shall occur at most once. The statement has no period and says shall. It is 44 characters. The flag is fatal. The context is an invoice line or a credit note line. The published test counts cac:InvoicePeriod. That test string is the same as UBL-SR-08. The count comparison has a space before <= and a space after it.

## What to change

On an invoice line or a credit note line, send at most one invoice period.

## Illustration

Illustration of the condition in the official statement. Not an example published by the source.

**Fails the stated condition.** An invoice line has two invoice periods.

**Passes the stated condition.** An invoice line has one invoice period, or none.

## Published context and test

Copied from the source. Not reimplemented on this page.

```
cac:InvoiceLine | cac:CreditNoteLine
```

```
(count(cac:InvoicePeriod) <= 1)
```

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