How the assessment base for contributions is calculated

How the assessment base for contributions is calculated is a question that determines how much both self-employed persons (SZČO) and employees pay in insurance contributions. The assessment base is the amount from which social and health insurance contributions are calculated using percentage rates. Understanding the principle of the calculation helps you estimate your future contributions and plan your cash flow better. It is not a one-off figure – the assessment base is reviewed regularly and changes in line with how your income develops and with the statutory limits.

Assessment base of an employee

For an employee, the assessment base is usually their gross wage. It is used to calculate the insurance contributions paid by both the employee and the employer, each at their own rate. For social insurance, a maximum assessment base (cap) applies, above which no further contributions are paid.

• employee’s base = gross wage
• contributions are paid by both the employee and the employer
• social insurance has a maximum cap

Assessment base of a self-employed person

For a sole trader, the calculation is more complicated. It is based on the partial tax base from business income, which is adjusted (the insurance contributions paid are added back) and divided by a statutory coefficient. The result is the annual assessment base, from which the monthly amount of contributions for the following period is determined. This is precisely why the amount of your contributions changes from year to year – it is always tied to the most recently filed tax return and the income reported in it.

Calculation steps for a self-employed person

1. The partial tax base from business income is taken.
2. The social and health insurance contributions paid for the year in question are added to it.
3. The result is divided by the statutory coefficient and the number of months.
4. The resulting base is compared with the minimum and the maximum.

Minimum and maximum

If the calculated base falls below the minimum assessment base, contributions are calculated from the minimum. If it exceeds the maximum base for social insurance, they are calculated from the cap. Check the specific minimum and maximum amounts for the period concerned – they change every year in line with the average wage.

• the base never falls below the statutory minimum
• social insurance has an upper limit
• the figures are indexed every year

Impact of flat-rate expenses

For sole traders who claim flat-rate expenses, the assessment base is usually lower than for those with actual expenses at the same turnover, because the flat rate artificially reduces the tax base. This saves on contributions in the short term, but it also reduces your future benefits and pension. Conversely, those who report genuinely lower expenses and a higher profit pay more, but build up higher entitlements. So when choosing between flat-rate and actual expenses, do not compare only the tax, but also the impact on the assessment base and contributions – this is exactly where it pays to calculate several scenarios at once.

Why it matters

The assessment base determines not only how much you pay, but also how high your benefits will be – sickness benefit, maternity benefit or your future pension. A lower base means lower contributions, but also lower benefits. It is therefore a balance between an immediate saving and future protection, which needs to be weighed up consciously.

Summary

How the assessment base for contributions is calculated is directly linked to how your tax return is prepared and to the expenses you claim. At Bilvao, we calculate the options and advise you on which base makes sense in terms of both contributions and future benefits. Check the specific coefficients and limits for the current period.

Current figures (2026)

Minimum contributions of a self-employed person in 2026

Figures valid for 2026; check the current wording.

Related articles: Obligations towards insurers when closing a business, Contributions on dividends: when health insurance contributions are payable, Sick leave for self-employed persons and sickness benefits.

Frequently asked questions

What is a sole trader’s assessment base calculated from?

It is based on the partial tax base from business income, to which the insurance contributions paid are added; the result is divided by the statutory coefficient and the number of months. The resulting base is then compared with the minimum and maximum applicable for the period concerned.

Is an employee’s assessment base the same as their gross wage?

In most cases, yes – an employee’s assessment base is their gross wage, from which both social and health insurance contributions are calculated. For social insurance, however, a maximum assessment base applies, above which the contributions no longer increase.