[Bug]: Italian FatturaPA exporter does not enforce Telefono and Fax XSD length constraints

Open src/Layers/IT/BaseApp/Local/EServices/EDocument/ExportFatturaPADocument.Codeunit.al and inspect PopulateCompanyInformation, especially the Telefono and Fax serialization. Reproduce with phone and fax values shorter than 5 or longer than 12 characters, then validate the generated FatturaPA XML against the XSD. Done means emitted values comply with TelFaxType or non-compliant optional elements are omitted with the intended warning behavior.

Describe the issue

In the Italian localization, the FatturaPA exporter writes the company phone and fax numbers directly into the Telefono and Fax XML elements after only removing hyphens.

The current implementation is effectively:

TempXMLBuffer.AddNonEmptyElement(
    'Telefono',
    DelChr(CompanyInformation."Phone No.", '=', '-'));

TempXMLBuffer.AddNonEmptyElement(
    'Fax',
    DelChr(CompanyInformation."Fax No.", '=', '-'));

However, the FatturaPA XSD defines both Telefono and Fax using TelFaxType, which has a minimum length of 5 characters and a maximum length of 12 characters.

Business Central's source fields can contain values outside this range. The exporter does not validate or constrain them before serializing the XML.

As a result, Business Central can generate a FatturaPA document that is not valid against the official schema.

For example, entering a 13-character phone number results in the full 13-character value being written to <Telefono>, making the XML schema-invalid.

The same issue applies to Fax.

Expected behavior

Business Central should ensure that values emitted in the FatturaPA Telefono and Fax elements comply with the TelFaxType constraints defined by the FatturaPA XSD.

The exporter should not generate XML containing values shorter than 5 characters or longer than 12 characters.

The exact handling can be decided by the implementation, for example by validating the value before export or by applying schema-aware normalization/truncation where appropriate, or still, since both fields are not mandatory according to the XSD specification, emitting a warning when not compliant and stopping the serializer from adding the Telefono or Fax elements to the XML.

The standard Company Information phone and fax fields should not necessarily be restricted globally, because they are used outside the FatturaPA context. The FatturaPA-specific export logic should instead ensure that the serialized XML is compliant with the schema, if emitted.

Steps to reproduce

1. Open Company Information in an Italian Business Central company.

2. Enter a phone number longer than 12 characters, for example:

   1234567890123
   

3. Create and post a sales invoice for a customer configured for FatturaPA.

4. Generate/export the electronic invoice.

5. Inspect the generated XML.

The exporter writes:

<Telefono>1234567890123</Telefono>

The value exceeds the maximum length allowed by the FatturaPA XSD.

The same behavior can be reproduced with the Fax No. field.

A value shorter than 5 characters can similarly be emitted even though it also violates TelFaxType.

Additional context

The issue is in the Italian FatturaPA export implementation, currently in:

src/Layers/IT/BaseApp/Local/EServices/EDocument/ExportFatturaPADocument.Codeunit.al

The relevant code is in PopulateCompanyInformation, where Telefono and Fax are emitted using the Company Information fields with only hyphens removed.

Other parts of the same exporter already perform schema-aware serialization, for example by limiting several string values to the maximum length allowed by the FatturaPA schema.

Telefono and Fax should receive equivalent schema-aware handling so that the standard exporter cannot produce XML that fails FatturaPA XSD validation.

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• I will provide a fix for a bug