Many self-employed individuals in the Czech Republic focus mainly on filing their annual personal income tax return. However, for freelancers and sole traders, the tax return is usually only the first step.
After the Czech personal income tax return is filed, self-employed individuals usually also need to submit annual reports to:
- the Czech Social Security Administration — ČSSZ, and
- their Czech public health insurance company, if they are part of the Czech public health insurance system.
This is especially important after the electronic tax return deadline for 2025, which is 4 May 2026. If the tax return was filed electronically, the annual reports for social security and health insurance are generally due within one month after the tax return deadline. For many self-employed individuals, this means 4 June 2026.
Who needs to file these reports?
If you were self-employed in the Czech Republic in 2025, you will usually need to file an annual report with ČSSZ.
You may also need to file a health insurance report with your Czech health insurance company. However, this depends on whether you belong to the Czech public health insurance system.
This is why it is important to check not only your tax obligations, but also your social security and health insurance position.
When must the underpayment be paid?
Once the annual report is submitted, it may show either:
- an underpayment,
- an overpayment, or
- no balance due.
If the report shows an underpayment, it must generally be paid within 8 days after the report is submitted.
If the report is filed late, the payment deadline is generally linked to the date when the report should have been filed. This means that postponing the report does not necessarily postpone the payment obligation.
In practice, if you file the report and it shows an underpayment, it is safest to pay it immediately or within the following few days.
Monthly advances may also change
The annual reports do not only calculate the final insurance for the previous year. They also determine the new monthly advances for the following period.
This is one of the most common surprises for self-employed individuals in the Czech Republic.
The amount of the monthly advance may change after the annual report is filed.
Therefore, after submitting the reports, you should always check whether you need to update your standing orders or recurring bank payments.
Minimum advances are usually adjusted from January
There is one important exception.
If you pay only the statutory minimum advances, the minimum amounts are usually increased already from January of the relevant year. In this case, the filing of the annual report may not cause any further change in your monthly advance.
This means that for many self-employed individuals with lower profits, the advance has already been adjusted from January and the annual report does not create a further increase.
Why underpayments often happen even when you paid advances correctly
A frequent misunderstanding is that an underpayment means that the self-employed person has done something wrong or has an overdue debt.
That is not necessarily true.
The Czech system is based on advance payments. During the year, you pay monthly advances based on older data — usually based on the last annual report filed or you paid the minimum as a new freelancer. The final amount of insurance is calculated only after the year ends, when your real tax base is known.
This means that if your income increased during the year, your advances may simply not have been high enough to cover the final insurance.
Even if your income stayed roughly the same, an underpayment can still arise because the first months of the year were paid based on the previous reporting period. The new advances only start after the annual report is filed or after the deadline when it should have been filed.
So, if your report shows an underpayment, it does not automatically mean that you were in default during the year. It usually only means that the final insurance calculated from your actual annual income is higher than the advances already paid.
This is a normal part of the system.
Does an underpayment mean I have a debt?
Not in the usual “overdue debt” sense, as long as you pay it within the required deadline.
A balance due shown in the annual social security or health insurance report is a normal settlement of the previous year. If you pay it within the required 8-day deadline, it should not mean that you have an overdue debt.
This is important, for example, if you later need a confirmation that you do not have outstanding debts with the authorities.
The problem usually arises only if:
- the report is not filed,
- the underpayment is not paid on time,
- the monthly advances are not updated correctly, or
- payments are sent with an incorrect variable symbol or to the wrong account.
Practical example
A self-employed person filed their 2025 Czech tax return electronically on 30 April 2026.
They then submit their ČSSZ and health insurance reports in May 2026. The reports show that they should pay an additional CZK 18,000 for social security and CZK 9,000 for health insurance.
This does not automatically mean that they had been “in debt” during 2025. It means that their final insurance for 2025, calculated from their actual annual income, was higher than the monthly advances already paid.
They should now:
- pay the underpayments within 8 days after submitting the reports,
- check the new monthly advance amounts,
- update their standing orders,
- make sure future payments are sent with the correct details.
What should you check after filing the reports?
After filing your annual reports, do not just save the confirmation and move on. Always check:
- whether an underpayment must be paid,
- whether there is an overpayment,
- the new monthly advance for social security,
- the new monthly advance for health insurance,
- from which month the new advance applies,
- whether your standing order needs to be updated,
- whether you are sending the payment to the correct account with the correct variable symbol.
Final reminder
For self-employed individuals in the Czech Republic, the annual compliance process does not end with the personal income tax return.
You may also need to file the annual social security and health insurance reports, pay any underpayments within the required deadline, and update your monthly advances.
If a report shows an underpayment, do not panic. In many cases, this is simply how the Czech advance-payment system works. The key is to pay the balance on time and adjust the monthly payments for the next period.
Need help with Czech social security or health insurance reports?
We help self-employed expats in the Czech Republic understand their annual reporting obligations, calculate underpayments or overpayments, and set the correct monthly advances for the next period.