Missing a tax deadline in the Czech Republic isn't just inconvenient — it costs money. Penalties add up quickly. Here's exactly when you need to file, pay, and how to get extra time if you need it.
The Key Deadlines for 2026
April 1, 2026 — Standard Deadline
This is the baseline. If you're filing a paper return or submitting electronically without a data box, your 2025 tax return must reach the tax office by this date. The postmark counts if you're mailing it.
May 1, 2026 — Electronic Filing Extension
File through a data box (datová schránka) or with an electronic signature, and you automatically get an extra month. No application needed — the extension is built into the law.
This is one of the best reasons to set up electronic filing. An extra month can make a real difference when tax season gets busy.
July 1, 2026 — Tax Advisor Extension
Working with a registered tax advisor? Your deadline extends to July 1. However, your advisor must notify the tax office of their representation before the standard April deadline.
This three-month extension is a major benefit of professional help, especially for complex returns.
Payment Deadlines
Your tax payment is due on the same day as your filing deadline:
- April 1, 2026 — paper filing
- May 1, 2026 — electronic filing
- July 1, 2026 — with tax advisor
Important: the payment must arrive in the tax office's account by the deadline, not just be sent. Plan for bank processing time.
Tax Advance Payments for 2026
If your 2025 tax liability exceeded 30,000 CZK, you must pay advances during 2026:
- June 15, 2026 — first advance
- September 15, 2026 — second advance (only if tax over 150,000 CZK)
- December 15, 2026 — final advance
These are prepayments toward your 2026 taxes, calculated based on your previous year's liability.
What Happens If You're Late?
The penalty structure is designed to encourage timely filing:
- Days 1-5: No penalty (grace period)
- Day 6 onwards: 0.05% of owed tax per day
- Minimum penalty: 500 CZK
- Maximum penalty: 5% of tax or 300,000 CZK, whichever is lower
On a 50,000 CZK tax bill, being 30 days late costs 750 CZK. Not catastrophic, but easily avoidable.
Requesting an Extension
In exceptional circumstances — serious illness, extended travel, etc. — you can request a deadline extension from the tax office. The request must be submitted before the original deadline expires, and you need compelling reasons.
Extensions aren't automatic. The tax office evaluates each request individually.
Tips for Staying on Track
- Start collecting documents in January
- Set up a data box for the automatic one-month extension
- Consider a tax advisor for the three-month extension
- Put all deadlines in your calendar with reminders
- Don't wait until the last day — systems get overloaded
2026 Tax Calendar at a Glance
Here are all the key dates for the year:
- January 31: Annual employer tax settlement requests due
- February 15: Deadline to request annual settlement
- April 1: Standard tax return deadline
- May 1: Electronic filing deadline
- June 15: First tax advance payment
- July 1: Tax advisor filing deadline
- September 15: Second tax advance (if applicable)
- December 15: Final tax advance payment