Running a business alongside employment in Czechia — taxes and contributions

Starting something on the side of a steady job is completely normal in Czechia — and you don't have to leave your employment to do it. If you earn extra as a sole trader alongside your salary, you are carrying out what is called a secondary self-employed activity. That comes with one big advantage: the contributions are much lighter than for full-time business, because your main insurance is covered by your employer.

Even so, it does not come without a few obligations and a handful of figures worth knowing in advance. The overview below shows when and how much you really pay in social and health insurance, how income tax works, and where the most common mistake lies — the one that can make a side business needlessly expensive.

What a secondary activity is, and why it matters

Your business counts as a secondary activity when you have another main source at the same time — most often a job, but also parental leave, studies up to the age of 26, or drawing a pension. Your employment therefore remains your main insurance relationship, and the trade is "on top". That is exactly why contributions are lower for a secondary activity: you do not pay the minimum contributions of a full-time entrepreneur, but amounts based on your actual profit. How to set up a trade in the first place is covered in how to get a trade licence.

Social contributions: you pay once you earn enough

This is the biggest difference from a main activity. You pay social (pension) insurance on a secondary activity only if your annual tax base (roughly, your profit) exceeds the so-called decisive amount. For 2026 it is set at CZK 117,521. Stay below it and you pay nothing towards social insurance; go over it and you pay contributions on the profit above the statutory line.

In your first year of business you also do not pay any social insurance advances at all — you settle them retroactively in your statement according to reality. If the obligation does arise, the minimum monthly advance for a secondary activity in 2026 is CZK 1,574. For example: if you earn CZK 80,000 in net profit over the year on the side, you pay nothing towards social insurance; at a profit of CZK 150,000 you do, but only on the part above the decisive amount.

Health insurance: no minimum advances

A similar relief applies to health insurance. Because your employer is the one covering the "minimum", the minimum assessment base does not apply to you for a secondary activity. In practice this means you pay health insurance on the business only from your actual profit, not from an artificially set minimum — and in the first year without monthly advances, in a single settlement based on your statement. It is a fundamental difference from a full-time entrepreneur, who pays the minimum every month regardless of whether they earned anything.

Income tax and filing your own return

Business income is taxed together with the rest: the basic personal income tax rate is 15%. It is often worth applying flat-rate expenses — 60% of income for a free trade and 80% for skilled crafts and agricultural activities — so you are taxed on only part of your income and do not have to collect receipts. Importantly, once you run a business alongside a job, your employer will not do the annual reconciliation for you; you file your own tax return, declaring both your salary and your trade income. The deadlines and requirements are summarised in tax returns – deadlines and obligations.

What to watch out for

Two things can make a side business needlessly expensive. First: as an employee you generally cannot use the popular flat-rate tax — income from employment (an ordinary salary) rules out entering the flat-rate regime. So you are left with an ordinary return with flat-rate expenses, which for a side income usually works out well anyway; a comparison is offered in flat-rate tax vs actual expenses. Second: in your statement for the social security administration you must explicitly mark the activity as secondary. If you do not, the office automatically treats it as your main activity — and the contributions are then considerably higher.

Is it worth it?

For most people who want to earn extra alongside their job or test their own idea, a secondary activity is the ideal first step. The contributions are low and tied to what you actually earn, the risk is small, and a side income that takes off can later flow smoothly into full-time business. The key is simply not to forget the tax return and the correct marking of the activity — then it earns for you alongside your job without unpleasant surprises.

Frequently asked questions

Do I have to pay contributions if I run a business alongside a job?

Not always. You pay social insurance on a secondary activity only if your annual profit exceeds the decisive amount, which for 2026 is CZK 117,521. You pay health insurance on your actual profit with no minimum advances, and in the first year no advances are paid at all — they are settled retroactively based on your statement.

Can I use the flat-rate tax while employed?

Generally no. Income from employment (an ordinary salary) rules out entering the flat-rate regime, except for income taxed at source by withholding. As an employee you therefore file an ordinary tax return, in which you can apply flat-rate expenses.

Do I have to file my own tax return?

Yes. When you run a business alongside a job, your employer will not do the annual reconciliation for you. You file the return yourself, declaring both your salary and your trade income; you should also mark the activity as secondary in your statement for the social security administration.