Attachments, PDF and separate feed

How are e-invoice attachments handled, and may they be sent by email?

Short answer

e-invoice may include supporting documents in BG-24/BT-125 using the permitted MIME types, including PDF, PNG, JPEG, CSV, XLSX and ODS. A PDF attachment is not generally mandatory in Slovakia and does not replace the XML. A file sent separately by email is additional business communication; it is not part of the same Peppol delivery envelope and does not prove that it travelled with the e-invoice.

BG-24

Supporting documents

The attachment is intended to complement the statements in the invoice, not to replace the mandatory structured data.

BT-125

Embedded file

When an attachment is inserted, the MIME type and file name are recorded according to the Peppol rules.

PDF

Allowed, not required

The financial report confirms that a PDF or image attachment is possible but not a general obligation.

Outside the delivery envelope

A separate e-mail can complete the business process, but its attachment is not automatically attached to the delivered e-invoice.

What Peppol enables

Peppol BIS Billing uses the BG-24 group for additional supporting documents. A document can be embedded as a Base64 object or specified as an external reference. The current list of MIME types includes PDF, PNG, JPEG, CSV, XLSX and ODS.

Slovak rule for PDF previews

The Financial Administration states in its FAQs that, since the Peppol 3.0.20 hotfix, a PDF or image invoice may be added as an attachment, but a PDF attachment is not mandatory. The definitive e-invoice remains the structured XML file.

Separate email

The VAT Act does not prohibit business partners from sending a supporting document via another communication channel. However, if you send it separately by email, this document is not technically part of the same Peppol message. Proof of delivery of the e-invoice under Section 76a therefore does not automatically constitute proof of delivery of the separate email.

If the attachment is important for approval, verification or contractual fulfilment, it is safer to attach it to the e-invoice using a supported method or to include a unique external reference in the XML and retain separate proof of delivery.

Conclusion

Include an attachment in the supported e-invoice structure when it must travel and be evidenced with the invoice. Separate email neither replaces the XML nor forms part of the Peppol delivery evidence.

Legal and technical basis

Section 76a(2)(c) and (d) of the VAT Act
Financial Administration FAQ, technical examples Nos. 8 and 14
OpenPeppol BG-24, BT-125 and the official MIME code list