E-invoicing Q&A 2: invoice content, Peppol and corrective documents

Note: some of the rules are based on a draft amendment to the Slovak VAT Act currently before Parliament. Where the article relies on the draft, we say so explicitly.

Throughout the article, "digital postman" (digitálny poštár) refers to a certified Peppol service provider that delivers e-invoices on a company's behalf.

E-invoice content and reporting

Will the required invoice content change from January 2027?

Not significantly. The mandatory content of an invoice is still set out in Section 74 of the VAT Act. As before, invoices may also contain voluntary details, such as the due date, bank details or an order number, which the customer needs to approve and pay the invoice.

Which e-invoice data will the tax authority see?

For invoices sent through a digital postman, only the data specified by law is reported to the tax authority, not the whole invoice. This mainly includes:

• the VAT IDs of the supplier and the customer, or the customer's name if it is not a VAT payer
• the invoice number, the date of supply and the date of issue
• the quantity and type of goods, or the scope and type of services
• the tax base for each VAT rate, the unit price and the total VAT in euros
• references for special regimes, such as self-billing, reverse charge or the margin scheme
• for corrective documents, a reference to the original invoice

The data is reported not by the supplier but by its digital postman, so the supplier's obligation is fulfilled once the invoice is sent to the postman. The current wording of the law also imposes a reporting obligation on the customer, but the draft amendment, proposed by the Ministry of Finance, abolishes it.

Which issue date should the e-invoice show?

Under the tax authority's current interpretation, the issue date equals the date the invoice is sent through the digital postman. Many postmen therefore plan to fill in the issue date themselves, while others will set a daily cut-off time for same-day sending. When choosing a postman, ask how they will ensure this requirement is met.

How detailed must the description of goods or services be?

Describe the goods or services as agreed in the contract or order. According to the tax authority and the Ministry, under a contract for work it is enough to state that the invoice covers part of the work under the contract. A breakdown of unit prices can go into an attachment, which is not reported to the tax authority.

If you invoice by units of measure, for example per square metre, each item must be listed on a separate line with its unit price.

Can I attach files to an e-invoice?

Yes, with limits. The Peppol network should handle messages of up to about 100 MB, but individual postmen may set lower limits. Peppol also accepts only certain file formats: PDF, images or Excel files are allowed, for example, while Word documents are not. If you need attachments, check the size limit and format with your postman in advance.

Where can I see what an e-invoice looks like?

The tax authority has published a page visualising an e-invoice. For each part of the invoice it shows the PDF view alongside the corresponding XML, highlights the data required by the VAT Act, and for each field lists its mapping to the European standard, whether it is mandatory and how many times it may occur. It is a useful reference for the IT specialists setting up your e-invoicing.

The Peppol network

What is Peppol and who manages it in Slovakia?

Peppol is a European infrastructure for the secure exchange of electronic documents between businesses (B2B) and between businesses and public authorities. In Slovakia, the Financial Directorate acts as the Peppol Authority. It certifies service providers, i.e. digital postmen, and sets the rules for using the Peppol standard.

From January 2027, domestic e-invoices sent via Peppol must go through this network. Cross-border e-invoicing will only become mandatory from 1 July 2030 under the EU ViDA Directive.

How can I check whether I am registered in Peppol?

In the public Peppol Directory you can look up your own company and your business partners by tax ID (DIČ) or by full name including Slovak diacritics. Every registered entity is assigned a Peppol ID.

Also check the list of supported document types. Invoices and credit notes are assigned automatically. However, if you or your customer use self-billing, your postman must add these document types manually. Without them you can neither send nor receive self-billed invoices.

Can I send e-invoices abroad via Peppol?

Yes, on a voluntary basis. Peppol is used in other countries too, which is why the list of Slovak digital postmen includes foreign providers. Cross-border e-invoicing must, however, be agreed with your business partner in advance, and you need to confirm that your postman supports it.

Self-billing

Does anything change for self-billing?

The rules in the VAT Act remain the same. A customer may issue an invoice in the name and on behalf of the supplier only under a written agreement. The invoice is governed by the rules of the country where the supply takes place, and the supplier remains responsible for its accuracy and timeliness.

What is new is the technical process:

1. both the supplier and the customer have self-billing enabled in Peppol (set up by their postmen)
2. the customer issues the invoice with code 389 and sends it to its postman
3. the customer's postman delivers it to the supplier's postman, and the supplier receives it

The supplier does not send the invoice back to the customer, as that would create a duplicate. The supplier's postman reports it to the tax authority. A more lenient deadline applies to self-billed invoices: the data must be reported within five days of the e-invoice being issued.

Corrective documents

How do I correct an incorrect e-invoice?

An e-invoice that has been sent can no longer simply be swapped for another one. Nor can the customer reject it in Peppol: every invoice is received, even an incorrect one or one sent by mistake. The customer then proceeds as before, contacting the supplier and asking for a correction or cancellation.

The supplier then issues a corrective document in one of two ways:

• a credit note (code 381) followed by a new invoice, which is the most common approach
• a corrected invoice (code 384), proposed for correcting non-financial data, such as a missing order number or a wrong address, without changing the price, tax base or VAT

A corrected invoice with code 384 does not change the tax liability or the VAT return, but as a corrective document it must be included in the VAT control statement. A similar code is already used in Germany.

How do I reference the original invoice?

The reference goes in field BT-25, which is mandatory and reported to the tax authority. If a corrective document covers several invoices, BT-25 can be repeated for each of them.

For volume rebates that cover all invoices in a period, such as the fourth quarter, the tax authority accepts stating the last invoice in BT-25 and the period in the text. If the rebate covers only some invoices, each one must be referenced.

How should invoices issued in 2026 be corrected in 2027?

It depends on how the original invoice was sent. If it did not go through a digital postman, the corrective document can be issued the old way, and e-invoicing is optional. If it was sent via Peppol, even as part of testing in 2026, the corrective document must also go through a postman.

Practical questions

What if the customer is not registered in Peppol?

From January 2027, every customer that is a VAT payer, a taxable person or a legal entity that is not a taxable person must be able to receive e-invoices. If the supplier properly issues the e-invoice and sends it through its postman, it has met its obligation even if the customer cannot receive it for technical reasons. Responsibility shifts to the customer.

If the supplier then sends the same invoice by e-mail, for example, the tax authority considers that no new invoice is created; it is simply made available another way. The customer can still deduct VAT if the invoice complies with the law and the conditions in Sections 49 to 51 of the VAT Act are met. We therefore recommend checking your customers' readiness before the launch and reminding them of their obligation.

Does anything change for summary invoices and payment schedules?

The change mainly affects payment schedules. Until now, for recurring supplies such as rent or leasing, a payment schedule or payment agreement could replace an invoice. From January 2027 this will no longer be possible, and a summary invoice may only cover recurring supplies within a single month.

The concept of recurring supplies under Section 19(3) of the VAT Act remains, however. If you have agreed, for example, quarterly payments for energy or rent, you can continue issuing four invoices a year.

Is an e-invoice required for advance payments?

A payment request, i.e. a pro forma or advance invoice, is not a tax document and is outside e-invoicing. However, if from January 2027 you receive an advance payment from a domestic customer, a tax liability arises and you must issue an e-invoice for the payment received. Review your processes for receiving advance payments in particular.

Will penalties apply from January?

The draft amendment to the VAT Act provides for a grace period from January to June 2027. During this period, the tax authority would not penalise:

• sending an e-invoice through a postman after the 15-day deadline
• errors and inconsistencies in the XML data

Penalties will still apply, however, if you fail to choose a digital postman or do not issue invoices in XML format.

Want to know more?

The third part of our Q&A series eFaktúra v praxi will take place on 5 November 2026 at 10:00. If you need help setting up e-invoicing or with a specific situation in your company, the experts at Forvis Mazars in Slovakia are here to help. Follow us on LinkedIn so you don't miss invitations to future webinars and events.