Do not panic. The deadline for the tax return has passed and you missed it. Yes, it is a problem, and yes, it can be handled — and the sooner you act, the less it costs. Here is exactly what to do, which penalties are in play and how to keep them small. Read the whole thing: almost every section can save you money.
The five-day grace period — it may not be too late at all
The good news first. The Czech Tax Code (Act No. 280/2009 Coll.) sets, in Section 250(2), a grace period of five working days. File the return within five working days of the deadline and no late-filing fine arises at all. It is one of the most useful provisions in the whole Code, and one most people have never heard of.
In practice
- Paper filing for 2025 is due on 1 April 2026. File by 10 April 2026 — five working days, because Good Friday (3 April) and Easter Monday (6 April) are public holidays — and there is no fine.
- Electronic filing is due on 4 May 2026; 1 May is a public holiday, so the deadline moves past the weekend. File by 12 May 2026 (8 May is a public holiday) and again there is no fine.
- Filing through a tax adviser is due on 1 July 2026, with the same five extra working days.
Careful: five working days means five working days. Weekends and public holidays do not count. If the deadline falls on a Friday, you have until the following Friday.
If you are inside that window, stop reading and file now. Today. Come back when it is sent.
The 2025 filing deadlines
Before the penalties, make sure your deadline has actually passed. A surprising number of people are not sure which one applies to them.
- 1 April 2026 — the basic deadline for paper filing, in person at the tax office or by post.
- 4 May 2026 — the extended deadline for electronic filing, through a data box or through EPO. Since 2023 every OSVČ (self-employed person) has a data box set up by law, so most entrepreneurs fall under this deadline.
- 1 July 2026 — the deadline when a tax adviser files for you. The power of attorney has to reach the tax office by 1 April 2026.
If you have a data box and file electronically, your deadline is 4 May 2026, not 31 March. Many self-employed people spend March in a panic while they actually have a month more. Check which deadline is yours before you assume the worst.
The fine for late filing
If the grace period has gone, the fine for a late tax assertion under Section 250 of the Tax Code applies. It works like this:
| Parameter | Value |
|---|---|
| Rate | 0.05 % of the assessed tax for each day of delay (0.01 % for a tax loss) |
| Threshold | A fine that does not exceed CZK 1,000 is not imposed; a minimum of CZK 500 applies only if you do not file even after being prompted |
| Maximum fine | 5 % of the assessed tax, and no more than CZK 300,000 |
A worked example
Your 2025 tax is CZK 150,000 and you file 30 days after the grace period runs out.
Fine: 150,000 x 0.05 % x 30 = CZK 2,250
At 90 days late: 150,000 x 0.05 % x 90 = CZK 6,750
The cap is 5 % of 150,000 = CZK 7,500, so in this case the fine can never exceed CZK 7,500.
If your tax is small — CZK 5,000, say — 0.05 % of CZK 5,000 is CZK 2.50 a day, so 30 days late comes to CZK 75. A fine that does not exceed CZK 1,000 is not imposed at all under Section 250(3) — it is a threshold, not a minimum. A minimum fine of CZK 500 applies only if you do not file even after the tax office prompts you.
The special case of nil tax
Even when no tax comes out — you are claiming a tax loss, or the credits cover the whole liability — a fine can still arise if you do not file even after being prompted (at least CZK 500 under Section 250(4)). You have to file the return even when you owe nothing, as long as you meet the statutory conditions for filing: income above CZK 50,000, a loss, employment alongside self-employment and so on.
Late payment interest is a separate penalty
The fine for late filing and the interest on late payment are two independent sanctions. File on time but pay late and the interest runs. Pay on time but file late and the fine arises anyway.
How the interest is calculated
Under Section 252 of the Tax Code the interest is the ČNB repo rate in force on the first day of the relevant half-year plus 8 percentage points, charged on the outstanding amount for every day of delay. The repo rate was 3.50 % in the first half of 2026 (interest of 11.50 % a year) and 3.75 % from 19 June 2026, so from 1 July 2026 the interest is roughly 11.75 % a year, or about 0.032 % a day. The examples below use the second-half rate as an approximation.
A worked example
You owe CZK 150,000 and pay 60 days late. Interest: 150,000 x 11.75 % / 365 x 60 = approximately CZK 2,897.
Six months late, at 180 days: 150,000 x 11.75 % / 365 x 180 = approximately CZK 8,692.
Together, the fine and the interest add up faster than people expect. On tax of CZK 150,000 and three months of delay you are looking at roughly CZK 11,000 in fines and interest combined.
What to do now: five steps
Step 1: File as soon as you can
Every day of delay adds to the fine. File today, even if the return is not perfect. You can correct it later with a supplementary return, and filing stops the fine from growing. An imperfect return filed now beats a perfect one filed in three weeks.
How to file:
- Data box — the fastest route. Log in at mojedatovaschranka.cz, fill in the form in EPO (the electronic filing service of the tax administration) and send it from the data box. Delivery is practically instant and you get proof that you sent it.
- EPO with an electronic signature — through the MOJE daně portal at adisspr.mfcr.cz. You need a qualified electronic signature.
- In person at the tax office — take the completed form to the filing room and have your copy stamped. Note that the paper deadline is the earlier one, so if you missed 1 April, filing on paper is still possible but the penalty runs from that original date.
- By post — the date of dispatch counts, not the date of delivery. Send it registered so that you have proof.
Step 2: Pay the tax immediately
The fine and the interest are independent, so even if the return goes in late, pay as soon as you can. Every day without payment adds interest. You can pay:
- By bank transfer to the tax office account — the account number is on the tax administration website and differs by tax type and region
- In cash at the tax office cash desk
- By postal order, allowing for the time the payment takes to arrive
Do not forget the right variable symbol: your birth number for individuals, or the IČO (business ID) for companies.
Step 3: If you cannot pay the whole amount
If a single payment is out of reach, you have two options:
- An instalment schedule (Section 156 of the Tax Code) — you can ask the tax office for permission to pay in instalments. For as long as the schedule runs, the interest drops to half of the late-payment interest (Section 253 of the Tax Code). Instalments can be spread over several years.
- Deferral of the tax (Section 156 of the Tax Code) — the whole payment is postponed to a later date. You have to show that paying at once would cause you serious harm. The interest rate drops here too.
Apply for an instalment schedule or a deferral as early as you can. The tax office normally decides within 30 days. State why a single payment is impossible and propose a concrete schedule — amounts and frequency.
Step 4: Check what else you have missed
As an OSVČ you have more than the tax return to file:
- The přehled — annual statement of income and expenses — for the social security office (ČSSZ), within one month of the deadline for the income tax return
- The same statement for your health insurance company, on the same timing
- VAT returns and the VAT control report, monthly or quarterly, if you are a registered VAT payer
If you missed the tax return, the odds are you missed these too. Check, and file them as well.
Step 5: Decide whether to file alone or with help
If you are unsure how to complete the return, consider an accountant or a tax adviser. A mistake in a return that is already late is a double problem: you pay the delay penalty and then risk an additional assessment and a penalty for the wrong figures on top.
Can the deadline be extended retroactively?
Generally no. The deadline for an ordinary tax return cannot be extended after the fact. There is one important exception.
The tax adviser and the power of attorney
If you engage a tax adviser to prepare the return and the power of attorney reaches the tax office by the original deadline — 1 April for paper filing, for instance — the deadline automatically moves to 1 July. But the power of attorney has to arrive in time; it cannot be done retroactively.
If you are already late, a tax adviser will not give you the deadline back, but can help you complete the return quickly and correctly and deal with the tax office. A simple personal income tax return costs somewhere around CZK 2,000 to 5,000 with an adviser, which pays for itself if it keeps errors out of the return.
An individual extension (Section 36 of the Tax Code)
The tax administrator can extend the filing deadline by up to three months at the taxpayer's request. But the request has to be made before the deadline expires. If you have already missed it, this route is closed. Keep it in mind for next year: if you can see you will not make it, ask in time.
Waiver of the penalty in exceptional cases
Section 259 of the Tax Code allows the tax administrator to waive tax accessories — fines and interest — where the delay had an excusable cause. Causes that are generally accepted:
- Serious health reasons, such as hospitalisation or serious illness, supported by a medical report
- A natural disaster, a flood or a fire affecting the taxpayer
- The death of a close family member around the time of the deadline
- A demonstrable system failure, such as the data box service or EPO being down on the last day of the deadline
The request has to be in writing with the reasons documented, and the tax office assesses it case by case. There is no legal entitlement to a waiver, but a well-founded request often succeeds. The request carries an administrative fee of CZK 1,000.
What does not count as an excusable cause
The tax office will generally not accept:
- Being busy, or forgetting
- Not knowing about the deadline — "I did not know I had to file"
- Problems with your accountant or tax adviser: the responsibility remains yours
- Technical problems on your side, such as a broken computer or lost access to the data box
The total bill for filing late
To see what is actually at stake, take a self-employed person with tax of CZK 100,000 who files and pays 60 days after the deadline:
- Late-filing fine: 100,000 x 0.05 % x 55 days (60 minus the 5 days of grace) = CZK 2,750
- Late-payment interest: 100,000 x 11.75 % / 365 x 60 = CZK 1,932
- Total: CZK 4,682
At six months late the total rises to roughly CZK 10,000 to 12,000 — money that keeping the deadline would have kept in your account.
How to avoid this next year
Prevention is the cheaper strategy. A few practical points:
- Start in January — do not wait for the last week. From January you have the previous year's figures, and most of what you need is available from the very start of the year.
- Collect documents as you go — ask your employer, bank and insurers for confirmations at the beginning of February. Banks typically need two to three weeks to issue a confirmation of interest paid.
- File electronically — it buys you a month over the paper deadline. As an OSVČ you have a data box anyway, so electronic filing is the natural choice.
- Set reminders — calendar entries for the key dates: 15 February (confirmations from employers), 1 March (start preparing), 15 March (finish), 1 April (paper deadline), 4 May (electronic deadline). The tax deadline calendar has the rest of the year's dates.
- Keep your records current — if your income and expenses are in order all year, the return is a matter of hours rather than days, with no frantic hunt for lost invoices.
All of that comes down to one sentence: keep your records as you go and file electronically. Then no deadline catches you out, and the five-day grace period stays what it should be — a reserve, not a rescue.
Official sources
- Section 250 of Act No. 280/2009 Coll., the Tax Code — fine for a late tax assertion
- Section 252 of the Tax Code — late payment interest
Taxorio scope: Taxorio provides invoicing and income/expense records for Czech sole traders. It is not full accounting or personalised tax advice. For an unsupported or unusual case, verify the treatment with a Czech accountant or tax adviser before filing.