# BR-DEC-01: Write the document allowance amount with no more than two decimals

A document-level allowance amount has more than two digits after the decimal point. Write it with two at most: `1.00` passes, `1.000` fails.

- Layer: EN 16931
- Severity: fatal (the document is invalid)
- Topics: Allowances and charges
- Official definition: https://docs.peppol.eu/poacc/billing/3.0/rules/ubl-tc434/BR-DEC-01/
- Explanation last updated: 2026-09-24

## The short answer

`BR-DEC-01` fails when the `cbc:Amount` of a document-level allowance, a `cac:AllowanceCharge` directly under the root with `cbc:ChargeIndicator` of `false`, has more than two characters after the decimal point. Round the allowance to two decimals and write it with no more.

The recorded `1.000` equals `1.00` as a number and still fails, because the check reads the text as written. `UBL-DT-01` is reported for the same `cbc:Amount`, since it applies the same two-decimal limit to amounts generally.

## What the rule checks

The rule selects each `cac:AllowanceCharge` that is a direct child of the `Invoice` or `CreditNote` root and whose `cbc:ChargeIndicator` is `false`, takes the text of its `cbc:Amount`, and counts what follows the first full stop. More than two characters fails.

A whole number has nothing after a decimal point to count; when tried, a document allowance of `1` validated cleanly.

Every character after the point counts, digits or not. When tried, `1.00` followed by a space inside the element failed this rule, although the schema accepts it as a number.

Neighbouring amounts have rules of their own. A document-level charge is `BR-DEC-05`, the allowance base amount is `BR-DEC-02`, and allowances on a line are `BR-DEC-24`. When tried, a document charge of `3.500` reported `BR-DEC-05` and `UBL-DT-01`, not this rule.

| Term | Meaning | UBL element |
|---|---|---|
| BT-92 | Document level allowance amount | `cac:AllowanceCharge/cbc:Amount (where cac:AllowanceCharge/cbc:ChargeIndicator is false)` |

## How an integration ends up here

Possible causes, from the shape of the rule rather than from measured usage:

- The discount is stored with three or four decimal places and serialised at the full scale of the column.
- One number formatter serves the whole document and is set to the precision the unit prices need.
- The allowance is a percentage of a total and is written before rounding. When tried, an unrounded `1.005` also broke `BR-CO-11`, because the allowance total of 1.00 no longer matched it.

## How to fix it

1. Round the allowance amount to two decimals once, when it is calculated, using the rounding your invoicing rules specify.
2. Format the value with at most two decimals and no surrounding whitespace, and write it to `cbc:Amount` in the document-level `cac:AllowanceCharge`.
3. Build `cbc:AllowanceTotalAmount` from the rounded allowance amounts, then the total without VAT from that, so every figure agrees with what is written.
4. If the allowance is a percentage of a base amount, write the base with two decimals as well; it has its own limit.

## Before and after

These are fragments, not complete documents. The complete synthetic documents they come from are linked below.

Fragment of the failing invoice: the document discount is written as 1.000

```xml
<cac:AllowanceCharge>
  <cbc:ChargeIndicator>false</cbc:ChargeIndicator>
  <cbc:AllowanceChargeReasonCode>95</cbc:AllowanceChargeReasonCode>
  <cbc:AllowanceChargeReason>Example document discount</cbc:AllowanceChargeReason>
  <cbc:Amount currencyID="GBP">1.000</cbc:Amount>
  <!-- tax category omitted from this fragment -->
</cac:AllowanceCharge>
```

Fragment of the corrected invoice: the same discount written as 1.00

```xml
<cac:AllowanceCharge>
  <cbc:ChargeIndicator>false</cbc:ChargeIndicator>
  <cbc:AllowanceChargeReasonCode>95</cbc:AllowanceChargeReasonCode>
  <cbc:AllowanceChargeReason>Example document discount</cbc:AllowanceChargeReason>
  <cbc:Amount currencyID="GBP">1.00</cbc:Amount>
  <!-- tax category omitted from this fragment -->
</cac:AllowanceCharge>
```

Only the text of the allowance `cbc:Amount` differs: `1.000` in the failing invoice, `1.00` in the corrected one, which is the same value. The allowance total and the other totals were built on 1.00, so none of them is disturbed. The failing document reports two EN 16931 findings for the one element: `BR-DEC-01` located at the `cac:AllowanceCharge`, and `UBL-DT-01` located at its `cbc:Amount`. `UBL-DT-01` limits every element whose name ends in `Amount` to two decimals, leaving out only the item net price and allowances inside `cac:Price`, so a document allowance that fails this rule fails that one too. Writing two decimals clears both.

### What the validator reported

- The failing invoice reports **BR-DEC-01** and [UBL-DT-01](https://ironfang.uk/docs/finance/rules/UBL-DT-01.md). The corrected document passes every layer with no findings.
  - [Download the failing XML](https://ironfang.uk/finance/rule-examples/BR-DEC-01-invalid.xml)
  - [Download the corrected XML](https://ironfang.uk/finance/rule-examples/invoice-rich.xml)

Recorded on phive 12.1.0 / phive-rules-peppol 4.5.6 / Saxon-HE 12.10, the engine behind the free validator, using synthetic data. A recorded result is regression evidence for these documents; it is not a certification.

## Where it applies

- Applies to UBL `Invoice` and `CreditNote`. When tried, a credit note with a document allowance of `1.000` reported the same pair of findings.
- The count is the same for every currency, including ones whose minor unit is not two digits, because `currencyID` plays no part in it.
- A decimal comma never reaches this rule. When tried, `1,00` failed the XSD layer and the EN 16931 and Peppol layers were skipped.

## Related rules

- [UBL-DT-01 is reported beside this rule, applying the same limit to every amount element](https://ironfang.uk/docs/finance/rules/UBL-DT-01.md)
- [BR-CO-11 checks that the allowance total equals the sum of the document allowances](https://ironfang.uk/docs/finance/rules/BR-CO-11.md)
- [BR-DEC-24 is the same limit for allowances on a line](https://ironfang.uk/docs/finance/rules/BR-DEC-24.md)
- [PEPPOL-EN16931-R040 checks an allowance amount against its base amount and percentage](https://ironfang.uk/docs/finance/rules/PEPPOL-EN16931-R040.md)

## Scope and source

Written for Peppol BIS Billing 3.0.21 (May 2026), EN 16931 1.3.16, as applied to UBL 2.1 Invoice and CreditNote documents. Other profiles, syntaxes and releases can define this identifier differently. Guidance version 2026-09-24.1: source checked 2026-09-24, explanation last updated 2026-09-24.

[The official definition of BR-DEC-01](https://docs.peppol.eu/poacc/billing/3.0/rules/ubl-tc434/BR-DEC-01/) carries the normative wording and test. This page is our explanation of it, not a copy.

Guidance does not change the engine verdict. Fixing this finding does not mean the document passes every layer, and validation does not certify legal or tax compliance or transmit a document over Peppol.

## Links

- [This rule as a web page](https://ironfang.uk/docs/finance/rules/BR-DEC-01)
- [Free Peppol invoice validator](https://ironfang.uk/tools/peppol-validator)
- [Rule index](https://ironfang.uk/docs/finance/rules.md)
- [Ironfang Finance API docs](https://ironfang.uk/docs/finance)
- The same rule is available to MCP clients as the tool `finance.rule.get` on https://mcp.ironfang.uk/mcp