ExemptionReason written to line item level violates EN16931 profile

[DevrimBaran]

When using Product.setTaxExemptionReason() with setTaxCategoryCode("E") in EN16931 profile, the <ram:ExemptionReason> element is written to both the line item (SpecifiedLineTradeSettlement) and the header (ApplicableHeaderTradeSettlement).

However, EN16931 only allows ExemptionReason in the header (BG-23 VAT breakdown), not on line item level. Validators reject this with:

From https://portal3.gefeg.com/invoice validator:

Das Element 'ram:ExemptionReason' soll in diesem Kontext nicht verwendet werden. [Zeile 68]

Steps to reproduce:

Invoice invoice = new Invoice()
    .setNumber("TEST-001")
    .setIssueDate(new Date())
    // ... sender/recipient setup ...
    .addItem(new Item(
        new Product("Insurance", "", "C62", BigDecimal.ZERO)
            .setTaxCategoryCode("E")
            .setTaxExemptionReason("Exempt under §4 UStG"),
        new BigDecimal("100.00"),
        new BigDecimal("1")
    ));

ZUGFeRDExporterFromA1 exporter = new ZUGFeRDExporterFromA1();
exporter.setProfile(Profiles.getByName("EN16931"));
exporter.setTransaction(invoice);
exporter.export("output.pdf");

Actual Result:

<!-- Line item - INVALID for EN16931 -->
<ram:SpecifiedLineTradeSettlement>
    <ram:ApplicableTradeTax>
        <ram:ExemptionReason>Exempt under §4 UStG</ram:ExemptionReason>  <!-- WRONG  -->
        <ram:CategoryCode>E</ram:CategoryCode>
    </ram:ApplicableTradeTax>
</ram:SpecifiedLineTradeSettlement>

<!-- Header - OK -->
<ram:ApplicableHeaderTradeSettlement>
    <ram:ApplicableTradeTax>
        <ram:ExemptionReason>Exempt under §4 UStG</ram:ExemptionReason>  <!-- CORRECT -->
        <ram:CategoryCode>E</ram:CategoryCode>
    </ram:ApplicableTradeTax>
</ram:ApplicableHeaderTradeSettlement>

Expected result:
ExemptionReason should only appear in ApplicableHeaderTradeSettlement, not in SpecifiedLineTradeSettlement when using EN16931 profile.
Workaround:
Post-process the XML to remove ExemptionReason from line items.
Version: 2.21.0

[jstaerk]

does this also apply to the factur-x extended profile?

[DevrimBaran]

I did not test extended profile, since I develop something where only EN16931 is needed. But if the same mechanic and rule is in there too it needs to be checked too I guess.