This page is general information, not tax advice. If the amounts are large or the situation feels complicated, talk to a tax lawyer before you file.
What matters is that you move first
A correction on your own initiative, filed before Skatteverket has contacted you about the matter, normally does not lead to a tax surcharge (skattetillägg). Once Skatteverket has already reached out or announced an audit, the correction no longer counts as voluntary, and the surcharge can apply.
The tax and the interest are due either way. What is at stake is the surcharge, and that is reason enough to do it before someone else does it for you.
How far back
Skatteverket can normally reassess six years back, counted from the end of the calendar year in which the tax year ended. In practice that means that during 2026 you can correct 2020 onward. Kfyran computes the whole period.
How to do it
- Export the full history from your broker. Most platforms export arbitrary date ranges. Request the whole period in one file per account, and keep the originals.
- Upload everything to Kfyran. Trades are sorted by close date in Swedish time, so you do not need to split the files by year.
- Go through one year at a time. Kfyran shows the K4 figures per year and converts every trade at the Riksbank rate for that exact day.
- File one correction per year. Each year is its own request for reassessment. You get SRU files and a cover letter for every year - in Swedish, because the K4 is a Swedish form.
- Describe what you are correcting. The cover letter states what was added, which accounts it concerns and how the amounts were converted. A case officer who understands the records rarely needs to ask.
- Expect interest. Late-payment interest (kostnadsränta) accrues on amounts paid late. It is not a penalty; it follows from the tax being paid later than it should have been.
Common worries
Will this be reported to the police?
A voluntary correction filed before Skatteverket has acted does not normally lead to prosecution. That is the point of correcting on your own initiative. For very large amounts, talk to a lawyer first anyway.
I lost money - do I still have to?
Yes. Losses must be declared too, and they can be worth money to you through deductions. Skipping a losing year means giving up the deduction and leaving an incomplete return at the same time.
I no longer have the statements
Contact the broker. Most keep the history for years and can send an export even for closed accounts.
Start by uploading your history. Import and computation are free, so you can see how large the amounts actually are before you decide.