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KPiR or flat-rate tax in 2026: how to choose the form of taxation

Expert knowledge. Content verified: 7 November 2026.

When running a one-person business, you choose the form of taxation, and with it the books: on the tax scale and flat 19% tax you generally keep the tax revenue and expense ledger (KPiR), and under flat-rate tax a revenue ledger. No form always wins: flat-rate tax is calculated on revenue without costs, while the scale and flat 19% tax are calculated on income, so the result depends on the flat rate for your activity and on the level of costs. Below are the rules for 2026, checked against the texts of the acts.

The three forms of taxation in brief

  • Tax scale: 12% of the tax base up to 120 000 PLN reduced by the tax-reducing amount of 3600 PLN, and on the excess over 120 000 PLN the tax is 10 800 PLN plus 32% of the excess (art. 27 para. 1 of the PIT Act). The scale applies if you do not choose another form (art. 9a para. 1).
  • Flat 19% tax: 19% of income from non-agricultural business activity (art. 30c para. 1 of the PIT Act). You choose it by declaration.
  • Flat-rate tax on recorded revenue: a rate calculated on revenue, without reducing it by deductible costs (art. 12 para. 2 of the Flat-Rate Tax Act).

Flat-rate tax: rates, limit and exclusions

The flat rate is determined by the type of activity, and the catalogue is in art. 12 of the Flat-Rate Tax Act (most often according to the PKWiU classification). The act provides for rates from 2% to 17%, for example:

  • 3%: including trade and catering (excluding beverages with an alcohol content above 1,5%).
  • 5,5%: including manufacturing and construction works.
  • 8,5%: including other services and education (for accommodation and property rental, 8,5% up to 100 000 PLN and 12,5% on the excess).
  • 12%: including software-related services.
  • 14%: including healthcare and architectural and engineering services.
  • 15%: including wholesale brokerage. 17%: liberal professions.

With several rates, the ledger shows revenue by rate. Before choosing flat-rate tax, check the conditions:

  • Limit: you can pay flat-rate tax in a given year if your revenue in the previous year did not exceed 2 000 000 euro (art. 6 para. 4 of the Flat-Rate Tax Act). The amount is converted at the average NBP rate from the first working day of October of the previous year (biznes.gov.pl). If you start a business during the year, you can pay flat-rate tax regardless of the amount of revenue.
  • Exclusions (art. 8 para. 1): including pharmacies, buying and selling foreign currency, trade in motor vehicle parts and accessories, and the production of excise goods (except electricity from renewable sources).
  • Services for a current or former employer within the same scope of activities that you performed or perform as an employee cause loss of the right to flat-rate tax in that year (art. 8 para. 2).

The health contribution in 2026 depends on the form

The health contribution is calculated differently in each form, so it must not be left out of the comparison. According to ZUS information of 2 February 2026:

  • Flat-rate tax: the base depends on cumulative revenue from the start of the year. Up to 60 000 PLN the contribution is 498,35 PLN per month (base 5 537,18 PLN), from 60 000 PLN to 300 000 PLN it is 830,58 PLN (base 9 228,64 PLN), and above 300 000 PLN it is 1 495,04 PLN (base 16 611,55 PLN).
  • Tax scale and flat 19% tax: the base is the income from the preceding month, not less than 4 806 PLN, so the contribution will not fall below 432,54 PLN for the months from February 2026 to January 2027.
  • Deductions: under flat-rate tax you deduct 50% of the health contributions paid from revenue (art. 11 para. 1a of the Flat-Rate Tax Act), and under flat 19% tax you deduct contributions from income up to an annual limit, which is raised every year and announced by notice (art. 30c para. 2 point 2 and para. 2b–2c of the PIT Act).

Deadlines you need to know

  • Declaration of flat-rate tax or flat 19% tax: by the 20th day of the month following the month of the first revenue in the tax year, and if the first revenue appears in December, by the end of the year. For revenue from January that is 20 February. The choice also applies to subsequent years until you give it up (art. 9 of the Flat-Rate Tax Act, art. 9a para. 2 and 2b of the PIT Act).
  • Advances: monthly by the 20th day of the following month, for December by 20 January. Quarterly payment is available to, among others, small taxpayers and those starting a business, and on the flat-rate tax also to taxpayers with revenue in the previous year of up to 200 000 euro (art. 44 para. 3g and 6 of the PIT Act, art. 21 para. 1–1b of the flat-rate tax act).
  • Annual return: from 15 February to 30 April of the following year (art. 45 of the PIT Act, art. 21 para. 2 of the flat-rate tax act).

What about the books: KPiR, revenue ledger, full accounting

  • You keep the KPiR under the regulation of 6 September 2025 (Dz.U. 2025 poz. 1299), in force from 1 January 2026. You enter invoice revenue no later than the 20th day of the month following the month in which it was earned (§ 11 para. 2), and after the month ends you total the data from columns 9–16.
  • You keep the revenue ledger under the regulation of the same day (Dz.U. 2025 poz. 1294): entries no later than the 20th day for the previous month (§ 6). You must also keep a register of fixed assets and keep purchase documents for goods (art. 15 para. 1 of the Flat-Rate Tax Act).
  • Full accounting is mandatory when net revenue from the sale of goods and products for the previous financial year was at least the equivalent of 2 500 000 euro (art. 2 para. 1 point 2 of the Accounting Act).

How to compare the forms using your own data

  1. Take the revenue and costs from the previous year or a realistic forecast for the new year.
  2. Find the flat-rate tax rate for your activity in art. 12 of the flat-rate tax act and calculate it on revenue, without costs.
  3. Calculate tax on the tax scale and flat 19% tax from income, i.e. revenue reduced by costs.
  4. Add the health contribution according to the rules of each form, and the deductions available under it.
  5. Check the limit of 2 000 000 euro and the exclusions from art. 8 before you choose flat-rate tax, and note the deadline for the declaration.

How it works in Zaksio

Anna and Kasia are software (an AI team), not an accounting firm or a tax adviser. In the company's tax profile you choose the legal form and the form of taxation, and Zaksio suggests how to keep the books: KPiR for the tax scale and flat 19% tax, a revenue ledger for flat-rate tax. An incompatible choice is blocked with an explanation. Zaksio does not choose the form of taxation for you and does not file the declaration of that choice: you do that yourself, in CEIDG or with the head of the tax office.

  • Entries in the KPiR or revenue register are created from sales and purchase invoices (including those downloaded from KSeF), payroll and depreciation, and you can add a manual entry yourself. You correct a mistake with a reversal entry, that is, an entry with a minus sign.
  • PIT-36, PIT-36L and PIT-28 advances and drafts are calculated from the ledger by deterministic, tested code, not by an AI model. They are drafts for review: you add your own contributions, reliefs and losses, and you or your accounting firm file the return.
  • The Start plan is free within limits; you can find their size in the Zaksio price list.

Sources

  • Act of 26 July 1991 on Personal Income Tax, consolidated text Dz.U. 2026 poz. 592 (art. 9a, 24a, 27, 30c, 44, 45) — https://isap.sejm.gov.pl/isap.nsf/DocDetails.xsp?id=WDU19910800350
  • Act of 20 November 1998 on the Flat-Rate Income Tax on Certain Revenues Earned by Natural Persons, consolidated text Dz.U. 2025 poz. 843 (art. 6, 8, 9, 11, 12, 15, 21) — https://isap.sejm.gov.pl/isap.nsf/DocDetails.xsp?id=WDU19981440930
  • Act of 29 September 1994 on Accounting, consolidated text Dz.U. 2026 poz. 522 (art. 2) — https://isap.sejm.gov.pl/isap.nsf/DocDetails.xsp?id=WDU19941210591
  • Act of 15 May 2026 amending the Act on Personal Income Tax, the Act on Corporate Income Tax and the Act on the Flat-Rate Income Tax on Certain Revenues Earned by Natural Persons (Dz.U. 2026 poz. 779) — https://isap.sejm.gov.pl/isap.nsf/DocDetails.xsp?id=WDU20260000779
  • Regulation of the Minister of Finance and Economy of 6 September 2025 on keeping the tax revenue and expense ledger (Dz.U. 2025 poz. 1299) and the regulation of the same day on keeping the revenue ledger and the register of fixed assets and intangible assets (Dz.U. 2025 poz. 1294) — https://www.gov.pl/web/finanse/publikacja-rozporzadzen-ministra-finansow-i-gospodarki-dotyczacych-ksiag-podatkowych
  • ZUS: Information on the contribution base and the amount of the health insurance contribution in 2026 (2 February 2026) — https://www.zus.pl/-/informacja-w-sprawie-podstawy-wymiaru-sk%C5%82adki-oraz-kwoty-sk%C5%82adki-na-ubezpieczenie-zdrowotne-w-2026-r.
  • Biznes.gov.pl: Flat-rate tax on recorded revenue — https://www.biznes.gov.pl/pl/portal/00263

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