Tax interest — basics

Tax interest is charged on tax arrears when a tax is paid late. This guide explains when it applies, how to calculate it and how to find the correct rate.

When tax interest applies

Usually from the day after the payment deadline. Each day of delay increases the amount.

How to calculate tax interest

arrears amount × annual rate × number of days / 365

Step‑by‑step

1. Determine the statutory deadline.
2. Determine the payment date.
3. Check the rate for the period.
4. If the rate changes, split the period.
5. Sum the parts.

Rates and changes

Rates are set by law and can change. If the rate changes during the delay period, calculate separately for each part.

Corrections and partial payments

If only part of the amount is paid, interest applies to the remaining balance. Corrections can affect the start date of interest.

Common mistakes

• wrong dates,
• outdated rate,
• ignoring rate changes.

Quick calculation

Use the tax interest calculator for an indicative result.

Do tax interest require a decision

In practice, interest arises by law, although authorities may show it in a decision or an arrears notice. The key factors remain the legal deadlines and rates.

When to seek help

If the arrears are large, the period is long or the rate changes, it is safer to verify the calculation with a specialist.

Reliefs and deferrals

If a taxpayer receives a deferral or installments, the interest calculation may change. Always verify the decision terms.

Short FAQ

• Is interest automatic? Usually yes, but it is often shown in a decision or notice.
• Can it be reduced? It depends on the legal procedure and requires a separate decision.