MIME types

Which attachment formats are permitted for an e-invoice?

Short answer

An e-invoice may include attachments in the following formats: CSV (text/csv), PDF (application/pdf), PNG (image/png), JPEG (image/jpeg), XLSX (application/vnd.openxmlformats-officedocument.spreadsheetml.sheet) and ODS (application/vnd.oasis.opendocument.spreadsheet). For each attachment, the mimeCode must match the file format and the supported subset of the IANA media type list under Peppol BIS Billing 3.0. Other formats, such as DOCX or ZIP, fail validation.

text/csv

Tabular text data

A common format for machine-readable supporting data.

application/pdf

Human-readable document

The most commonly used format for a human-readable attachment.

image/png, image/jpeg

Image attachments

For example, a scanned supporting document or a photograph.

XLSX / ODS

Spreadsheet formats

Both Excel and OpenDocument spreadsheet formats.

Detailed explanation

When an attachment is included, mimeCode is mandatory. A value outside the permitted list causes the XML document to fail validation under rules PEPPOL-EN16931-CL001 and BR-CL-24. Before attaching a file to an e-invoice, verify that its format is permitted. A commonly used business file format outside this list, such as a Word document or ZIP archive, will not pass validation.

How this follows from the law

The permitted mimeCode values come from the MimeCode code list used by Peppol BIS Billing 3.0. That specification implements the European standard EN 16931 for electronic invoicing and is the mandatory format for a Slovak e-invoice under Section 85o of Act No. 222/2004 Coll. on VAT.

Practical examples

A supplier attaches a detailed item breakdown in CSV format to an e-invoice.
A human-readable PDF preview is attached to make the content easier to review.
Validation under BR-CL-24 rejects an attempt to attach a ZIP or DOCX file.

Common mistakes

“Any type of file may be attached to an e-invoice.” Only the specified subset of MIME types in the MimeCode code list is permitted.
“The attachment format is not part of XML document validation.” A mimeCode value outside the permitted list causes validation to fail under rule BR-CL-24.
“Word documents and ZIP archives are commonly permitted e-invoice attachments.” These formats are not part of the permitted subset and will not pass validation.

Conclusion

An e-invoice attachment may be included only in CSV, PDF, PNG, JPEG, XLSX or ODS format; Peppol BIS Billing 3.0 validation rejects other file types.

Legal basis

Peppol BIS Billing 3.0, MimeCode code list (a subset of the IANA list)
Peppol BIS Billing 3.0, validation rules PEPPOL-EN16931-CL001 and BR-CL-24
Act No. 222/2004 Coll. on VAT, Section 85o