Tax Interest Calculator
Fast, accurate and free online tax interest calculator tool running directly in your browser.
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Other tools you may find usefulHow is interest on tax arrears calculated?
Interest for arrears is calculatedfrom the day following the tax payment deadline up to and including the payment date, according to the formula: amount of arrears × rate × number of days / 365. The result is rounded to whole zlotys. Our calculator automatically takes into account rate changes over time - if your arrears cover several periods of different rates, each section is counted separately, just like the tax office does.
Current interest rates (from March 5, 2026)
- basic rate - 10.50%per annum (200% of the NBP Lombard rate + 2%, not less than 8%),
- reduced rate - 5.25%(50% of the basic) - with submitting a legally effective correction of the declaration within 6 months and paying the arrears within 7 days,
- increased rate - 15.75%(150% of the basic) - applies to VAT and excise duty when the understatement was detected by the tax authority.
When is interest not paid?
No late payment interest is payable if the amount does not exceedPLN 8.70(three times the fee charged by Poczta Polska for ordering a letter item). Interest is paid without notice, together with the arrears, to your tax microaccount.
Example: how much interest on PLN 10,000 in arrears?
Let's assume a PIT arrears: PLN 10,000, the payment deadline was April 30, 2026, you pay on June 12, 2026. Days of delay: from May 1 to June 12 inclusive =43 days. Interest: 10,000 × 10.50% × 43 ÷ 365 = PLN 123.70 → after roundingPLN 124. At a reduced rate (correction on your own initiative + payment within 7 days) it would be PLN 62 - it is worth detecting the error yourself before the office does it.
History of late payment interest rates
| Validity period | Basic | Reduced | Increased |
|---|---|---|---|
| from March 5, 2026 | 10.50% | 5.25% | 15.75% |
| 4/12/2025 – 4/03/2026 | 11.00% | 5.50% | 16.50% |
| 9/10/2025 – 3/12/2025 | 11.50% | 5.75% | 17.25% |
| 3/07/2025 – 8/10/2025 | 12.00% | 6.00% | 18.00% |
| 5/10/2023 – 2/07/2025 | 14.50% | 7.25% | 21.75% |
| 7/09/2022 – 4/10/2023 | 16.50% | 8.25% | 24.75% |
The basic rate is 200% of the NBP Lombard rate + 2 p.p. (minimum 8%) - so it decreases with interest rate cuts. The calculator has a full history of rates built-in and divides the arrears period into sections.
Tax interest and ZUS and statutory interest
Please note three different types of interest:tax(Tax Ordinance - this calculator; Tax Office, PIT/CIT/VAT, also ZUS contributions calculated according to the same rates),statutory for delay(Civil Code - invoices and contracts between companies/consumers) andstatutory capital. They have different rates and legal bases - for civil settlements, use the statutory interest calculator and here you will only calculate arrears to the tax office. You direct the payment to yourstax microaccount.