An entrepreneur does not wait with income tax until year-end. During the year advances are paid — by the 20th day of the month following the month (or quarter) in which the revenue arose — and for December or the last quarter by 20 January. The annual return is filed between 15 February and 30 April, and any difference is paid in that same period. What matters, however, is not only "by when" but also "for which month" — and that depends on the date on which the revenue arose.
What determines the month in which the tax is paid
In a sole proprietorship, revenue arises as a rule on the day the goods are handed over or the service (or part of it) is performed, but no later than on the day the invoice is issued or payment is received — whichever event occurs first. The date the money hits the account therefore often does not matter.
An exception applies to services settled in periods, e.g. a monthly subscription or ongoing support under a cooperation agreement with another firm. If the parties set a settlement period in the contract or on the invoice, revenue arises on the last day of that period, no less often than once a year.
Example. A programmer finished the implementation on 27 March 2026, issued the invoice on 2 April and the client paid on 30 April. The revenue belongs to March, so the advance (on monthly settlement) must be paid by 20 April — before the money reaches the account.
Foreign clients and foreign-currency invoices
Where the invoice is issued in euros, dollars or pounds, revenue is converted into zloty at the average NBP rate from the last working day before the day on which the revenue arose. The same rule applies to costs in foreign currency — the rate of the working day before the day the cost is incurred is taken. The difference between the rate on the revenue day and the rate on the payment day does not change the advance deadline, but may give separate exchange differences to settle.
For entrepreneurs serving foreign clients, the practical conclusion is that payment deadlines are identical to those for domestic clients; only the way of determining the amount in zloty changes.
Monthly or quarterly
| Form of taxation | Who may pay quarterly | Where to choose |
|---|---|---|
| Tax scale or flat tax (podatek liniowy) | a small taxpayer (previous-year VAT-inclusive sales revenue up to the equivalent of EUR 2 million) and new businesses | information in the annual return for the year in which quarterly payments were made |
| Ryczałt on recorded revenue | new businesses and firms with previous-year revenue up to the equivalent of EUR 200,000 | information in the annual return |
On the scale and flat tax there is still a third option — simplified advances. A fixed monthly amount is then paid, equal to 1/12 of the tax calculated on the income from the return filed a year earlier (or two years earlier if there was no income a year ago). It must be applied for the whole year, and the settlement comes with the annual return. This makes planning easier, but with fast-growing revenue it means a large top-up in April.
The choice of taxation form has more influence on the amount of tax than on the deadlines. We describe the scale rules in the article General rules in PIT, and how to change the form — in the text on changing the form of taxation.
Payment calendar at the turn of 2026 and 2027
- Advance for October 2026 — by 20 November 2026 (Friday).
- Advance for November 2026 — 20 December falls on a Sunday, so the deadline moves to Monday 21 December 2026. When the last day of the deadline falls on a Saturday or a non-working day, the nearest working day counts.
- Advance for December or Q4 2026 — by 20 January 2027 (Wednesday).
- Annual return for 2026 (PIT-36, PIT-36L, PIT-28) — in the 15 February – 30 April 2027 period. A return filed earlier is deemed filed on 15 February.
- Top-up tax payment — before the deadline for filing the return, i.e. in practice by 30 April 2027.
With quarterly settlement, the advances for the successive quarters of 2026 fell on 20 April, 20 July and 20 October, and the last one — on 20 January 2027.
When there are no advances
- Unregistered business activity (działalność nierejestrowana) — no advances are paid during the year; revenue and costs are settled once in PIT-36 by 30 April.
- No income from the start of the year — on the scale and flat tax, the advance is calculated cumulatively, so if costs exceed revenue or earlier payments cover the liability, the advance for the given period is zero.
- Ryczałt — here there are no costs, so tax is due for every month with revenue.
Most common mistakes with deadlines
- Setting the revenue month by the payment date instead of the date of service performance or invoice issue.
- Converting a foreign-currency invoice at the rate from the day the money came in.
- Switching to quarterly payments despite exceeding the EUR 2 million limit (scale, flat tax) or the EUR 200,000 limit (ryczałt) in the previous year.
- Overlooking the weekend postponement — and the reverse: assuming the deadline moves to Monday when the 20th falls on a working day.
How Good Balance can help
As part of simplified accounting, we calculate the advances every month, watch the exchange rates for foreign-client invoices and prepare the annual return. We help those starting a firm choose the form of taxation and the way of payment when registering a sole proprietorship.