**If you file before the tax office writes to you, you pay a surcharge, not a penalty:** 1% of the tax plus 1% per full month late, 15% after twelve months, with late-payment interest from then on. The sooner you file, the less it costs.

- The surcharge is cut by **25%** if you pay the tax when you file, then the surcharge within the period the tax office's notice gives you.
- Late-payment interest: 4.0625% a year in 2026.
- Once the tax office has written to you, it becomes a **penalty**: 50% to 150% of the unpaid tax, plus interest.
- A late return with **zero tax** costs a fixed fine: €200, halved to €100 if you file before any letter.
- A return asking for a refund is never late within its four years.

## What to do now

File each missing return as soon as you can, owner by owner. See what each year costs with our free [missed-years calculator](https://casitatax.com/en/past-years/), or [let us catch up for you](https://casitatax.com/en/#start).