Most Polish sole proprietorships keep the tax revenue and expense ledger (podatkowa księga przychodów i rozchodów, KPiR) or, under the lump-sum tax (ryczałt), a revenue register. These are simple tools, but not suitable for everyone. As a business grows, the Polish Accounting Act at some point requires a switch to full, double-entry accounting books (księgi rachunkowe). The good news is that this moment can be predicted — and October is the best time to check whether it applies to your business.
What the threshold is and what determines it
A natural person running a business must keep accounting books if their net revenue from the sale of goods, products and financial operations for the previous financial year amounted to at least the equivalent of EUR 2,500,000. Until the end of 2024 the threshold was EUR 2,000,000 — it was raised from 2025.
Because the limit is set in euro, it is converted into zloty every year at the average NBP exchange rate from the first business day of October of the year preceding the financial year. In 2026 the amount is PLN 10,646,500 (rate of 1 October 2025: PLN 4.2586). Based on the NBP rate of 1 October 2026, the limit for 2027 will be approximately PLN 10,942,500 — almost PLN 300,000 more than a year earlier.
The same rule applies to partners in civil-law partnerships of natural persons (spółka cywilna), as well as general partnerships of natural persons (spółka jawna) and professional partnerships. Capital companies always keep accounting books, regardless of their size.
How to calculate revenue so you are not caught off guard
What counts is net revenue, i.e. excluding VAT, earned over the whole previous year. Exceeding the threshold during the year does not mean an immediate change of records — the obligation arises from 1 January of the following year. So if revenue for 2026 exceeds the limit for 2027, accounting books must be kept from the beginning of 2027.
In practice, it is worth adding up revenue from January to September now and estimating the last quarter, taking into account seasonality, large orders or planned sales of assets. Such a forecast lets you prepare the change calmly, instead of discovering it at year-end closing.
A separate issue is the lump-sum tax on recorded revenue (ryczałt) — it has its own, lower revenue limit under the Lump-Sum Income Tax Act. A business owner on ryczałt usually loses the right to this form of taxation before getting anywhere near the full accounting threshold, so both limits should be monitored in parallel.
What changes after switching to accounting books
The KPiR ledger is mainly used to determine income for personal income tax (PIT). Accounting books cover much more: business assets, receivables, liabilities, cash and equity. Every transaction is posted to accounts under the rules of the Accounting Act, and after the year ends financial statements are prepared and submitted electronically to the tax administration.
The form of taxation does not change — the business owner continues to settle tax under the progressive tax scale or the flat tax. What changes is the way records are kept: the accounting policy (polityka rachunkowości), the chart of accounts, settlements with counterparties and stocktaking become more important. It means more work, but also a clearer picture of the company's financial position, which is useful, for example, in talks with a bank.
Deadlines and formalities when switching
If the obligation results from exceeding the limit, the business owner does not file any application — the obligation arises by operation of law. Where the financial year is the calendar year, the books are opened as of 1 January, and the law allows 15 days from that date to do so.
The basis for opening the books is the opening balance sheet. To prepare it, you need to reliably determine the assets and their sources of financing as of the switch date: fixed assets, inventory, receivables, liabilities and bank balances. The year-end physical stocktaking (spis z natury) carried out by businesses keeping a KPiR ledger is helpful here. You also need to prepare an accounting policy and choose accounting software that supports full accounting.
Accounting books can also be kept voluntarily, even if revenue is below the limit. In that case, this information is given in the annual tax return for the year in which they were kept.
How to prepare already in the fourth quarter
Most problems arise when the switch is left to the last minute. In the last quarter of the year it is therefore worth: comparing your revenue forecast with the new limit, putting your fixed asset register and purchase documents in order, reconciling balances with your key counterparties and planning a thorough stocktaking as of 31 December. Well-prepared year-end data is, in practice, ready-made material for the opening balance sheet.
If revenue is close to the threshold, it is also worth considering whether a voluntary switch to accounting books would be wiser than a forced one in the following year — with dynamic growth this is often the case.