Calculation rules

`BR-CO-10`: Sum of line net amounts (BT-106) is wrong

BT-106 must equal the exact sum of all invoice line net amounts (BT-131).

Fact sheet

Rule: BR-CO-10
Severity: Error – the invoice is invalid
Rule set: EN 16931 – applies to XRechnung and ZUGFeRD/Factur-X
Affected fields: BT-106, BT-131
Syntax: CII & UBL

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Official wording

[BR-CO-10] Sum of Invoice line net amount (BT-106) = Σ Invoice line net amount (BT-131).

Source: official EN 16931 Schematron (CEN), as also applied to XRechnung and ZUGFeRD/Factur-X.

What the rule requires

The sum of invoice line net amounts (BT-106) must equal the sum of all invoice line net amounts (BT-131) exactly – to the cent, with no tolerance. The rule is part of EN 16931 and therefore applies to XRechnung as well as to ZUGFeRD and Factur-X.

Document-level allowances and charges (BG-20, BG-21) do not belong in BT-106; they only enter the invoice total without VAT (BT-109). Line-level discounts, on the other hand, are already included in the line net amount.

Common causes

Rounding: BT-106 is computed from unrounded values (quantity × price) while the lines are written rounded.
A discount on the whole invoice was already subtracted in BT-106.
Lines were removed or added later, but the sum was not recalculated.
Credit lines with negative amounts are missing from the sum.

What it looks like in XML

✗ CII – wrong

<ram:IncludedSupplyChainTradeLineItem>        <!-- line 1 -->
    … <ram:LineTotalAmount>300.00</ram:LineTotalAmount> …
</ram:IncludedSupplyChainTradeLineItem>
<ram:IncludedSupplyChainTradeLineItem>        <!-- line 2 -->
    … <ram:LineTotalAmount>49.99</ram:LineTotalAmount> …
</ram:IncludedSupplyChainTradeLineItem>
…
<ram:SpecifiedTradeSettlementHeaderMonetarySummation>
    <ram:LineTotalAmount>350.00</ram:LineTotalAmount>  <!-- BT-106: 300.00 + 49.99 = 349.99 -->
    …
</ram:SpecifiedTradeSettlementHeaderMonetarySummation>

✓ CII – correct

<ram:SpecifiedTradeSettlementHeaderMonetarySummation>
    <ram:LineTotalAmount>349.99</ram:LineTotalAmount>
    …
</ram:SpecifiedTradeSettlementHeaderMonetarySummation>

In UBL, BT-106 is cac:LegalMonetaryTotal/cbc:LineExtensionAmount.

Fix in C#

Round each line net amount to two decimals before setting it, then build the sum from exactly these values. With the Facturexa Creator:

// Compute BT-106 from the lines instead of keeping it separately
invoice.LineTotalAmount = invoice.TradeLineItems.Sum(l => l.LineTotalAmount);

Tip: check generated invoices with the Facturexa Validator before sending them – it reports BR-CO-10 offline inside your own application.

Related rules

All explained validation rules

BR-CO-10: Sum of line net amounts (BT-106) is wrong