What makes the first year of annual reporting frightening isn't complexity — it's how much has to be reconstructed. If the documents were collected as you went, it is a few evenings. If they were not, it is a month of correspondence with filling stations and toll operators.
Three reports, not one
The tax return is only one of the three documents. Alongside it go annual reports to social insurance (ČSSZ) and to your health insurance fund. All three have their own deadlines and their own forms, and all three rest on the same data.
The deadline is months, not a date
The tax code does not set a calendar date. It sets a number of months from the end of the tax period — and that number depends on how you file.
| How you file | Deadline (§ 136 daňového řádu) |
|---|---|
| Basic deadline | 3 months after the end of the tax period |
| Electronically, having not filed within 3 months | 4 months after the end of the tax period |
| Filed by a tax adviser, or accounts must be audited | 6 months after the end of the tax period |
Source: zákon č. 280/2009 Sb., § 136 — “Daňové přiznání […] se podává nejpozději do 3 měsíců po uplynutí zdaňovacího období.”
Two things people miss. The four-month extension is not an automatic right for anyone filing electronically: it applies only where you did not file within three months and then filed electronically. And the actual calendar day shifts with weekends and public holidays, so work to the number of months and check the date for the year in question — this article deliberately does not name one.
What has to be collected
Every invoice you issued during the year. All of them, including cancelled and corrected ones — the sequence has to be unbroken.
Cost documents. Fuel, tolls, ferries, rent, insurance, phone. For each one: the transaction date, the amount and the currency. Which of them actually reduce the base is worked through in Which costs actually reduce the tax base.
Bank statements. They tie the documents to the actual movement of money.
Evidence of the exchange rate. Costs in route currencies are converted at the ČNB rate for the transaction date — the rate has to be recorded with the amount, not picked out afterwards. In detail in How the ČNB rate works.
Start collecting in January
The one piece of advice that saves real days: once a week, file that week’s documents. Everything else in this article follows from that.
What happens after filing
The reports trigger a recalculation of the social and health insurance advances for the next period. For anyone who has just worked a full first year, this is usually the most noticeable item: the minimum advance of the first year is replaced by a calculated one. Plan for that jump when you file, not when the money leaves the account.
