Invoices and documents · 3 min read

DUZP — the date of taxable supply

What DUZP (the date of taxable supply) is, why it's crucial for sorting a supply into the right VAT period, how Taxorio pre-fills it, and when to change it by hand.

What DUZP is

DUZP — short for date of taxable supply (DUZP) — is the date on which the supply actually took place (goods delivered or a service provided). It's one of the mandatory particulars of a tax document under §29 odst. 1(h) of Act No. 235/2004 Sb., on VAT.

Why DUZP matters

DUZP determines which VAT tax period the supply belongs to. The rule is simple: VAT is declared in the period in which the DUZP fell — regardless of when the invoice was issued or when the client paid.

Example: you provide a service on March 28th (DUZP = March 28th), but you don't issue the invoice until April 5th. That supply still belongs in the VAT return for March (or Q1, if you're a quarterly payer), not April.

⚠️ Careful: An incorrect DUZP can mean VAT gets declared in the wrong period. During a tax audit, the tax authority may assess additional VAT plus late-payment interest.

How Taxorio pre-fills DUZP

When you issue a new invoice, Taxorio automatically sets the DUZP to the same date as the invoice issue date. This is the right setting in the vast majority of cases — especially when you issue the invoice on the day you provided the service. If the service was provided earlier, the earlier day belongs in DUZP: for a service, whichever of the two dates (provided vs. issued) came first always decides.

When to change DUZP

You need to adjust DUZP by hand in these situations:

  • Delivery of goods — DUZP is the date the goods were physically handed over to the buyer, not the invoice issue date. If you shipped the goods on April 20th and issued the invoice on May 2nd, DUZP = April 20th.
  • Completion of a job or project — for long-running jobs, DUZP is the date the output was handed over and accepted.
  • A recurring supply — for regular monthly invoices (rent, flat-rate services), DUZP is usually the last day of the month the supply covers. For a recurring invoice schedule, you switch this on once and Taxorio then sets DUZP to the end of the billed period on its own, on every invoice it issues.
  • An advance — a proforma invoice has no DUZP of its own (it isn't a tax document). For a VAT payer it's carried by the tax document for the received payment instead, which is created once the advance is confirmed, and it equals the day the payment arrived.

How to fix DUZP

A wrong DUZP is fixed by editing the document, never with a credit note — § 42 covers a change in the tax base, not a wrong date. But the form only opens for an unpaid invoice; for a paid one, first go through More actions → Clear payment, then fix the DUZP and mark the invoice paid again. There's no editing for a tax document for an advance: clear the advance's payment (the document gets cancelled) and confirm the advance again with the correct date — a new document with a new number is created.

⚠️ Moving DUZP between tax periods affects two periods. If you've already filed a return or a VAT control statement for either of them, work the fix through with your accountant — sometimes § 104 ZDPH is enough without any filing, other times a supplementary return and a follow-up control statement are needed.

DUZP for non-VAT payers

If you're not a VAT payer, you don't have to state DUZP on the invoice — this field isn't mandatory for non-payers in Taxorio. You can still fill it in for your own clarity, and in case your situation changes down the line.

💡 Tip: If you're not sure of the correct DUZP for a particular job, consult your tax advisor. Construction work or supplies with assembly in particular have their own specific rules.