Guide
What an invoice must include in 2026
The requirements depend on whether you're a VAT payer. The generator adjusts the fields for you. Here's what an invoice must show, and why.
Invoice from a non-VAT payer
In the Czech Republic, an invoice is an accounting document. It must show a document title and number, the supplier and customer, a description of the supply, the amount, the issue date, and the date of supply. As a business document, it also needs your name, registered office, Company ID, and register entry under Section 435 of the Czech Civil Code. In Slovakia, Section 3a of the Commercial Code requires your business name, registered office or place of business, legal form (for companies), Company ID, and register entry on business documents.
Tax invoice from a VAT payer
In the Czech Republic, Section 29 of the VAT Act adds the Tax IDs of the supplier and the customer, a document number, the taxable supply date, the unit price excl. VAT and any discount, the tax base, the rate, and the VAT amount. You must issue it within 15 days of the taxable supply or of receiving payment. In Slovakia, Section 74(1) of the VAT Act requires both parties' VAT IDs, a sequential number, the delivery date, the issue date, the unit price excl. VAT, the tax base, the rate, and the total VAT in euros, and Section 73 gives you 15 days from delivery or from receiving payment.
Proforma invoice
A proforma invoice is only a request for payment, not a tax document. In the Czech Republic, a VAT payer issues a tax document for the received payment within 15 days and bills the rest after delivery. In Slovakia, a VAT payer also invoices a payment received before delivery within 15 days (Section 73). That's why a proforma from the generator says “Not a tax document.”
Common mistakes
Based on Czech Act No. 235/2004 Coll., on VAT (Sections 28, 29, 30, and 35), Act No. 563/1991 Coll., on Accounting (Section 11), and Section 435 of Act No. 89/2012 Coll., the Civil Code, and on Slovak Act No. 222/2004 Coll., on VAT (Sections 73, 74, and 76), as amended in September 2026. Documents up to CZK 10,000 incl. VAT in the Czech Republic, or EUR 100 in Slovakia, can be issued as simplified invoices. Tax invoices are kept for 10 years in both countries.
- An s.r.o. leaves out its Commercial Register entry.
- A VAT payer forgets the Tax ID of a customer who is also a VAT payer.
- Invoice numbers don't follow one continuous sequence.
- VAT is calculated at the wrong rate, for example on drinks in a restaurant.
- An invoice in a foreign currency doesn't show the VAT converted to koruna (Czech Republic) or euros (Slovakia).