FAQ
A few common questions about how capi.tax works.
Is this tax advice?
No. capi.tax prepares your data; it does not give tax advice. It reads your broker export, converts the amounts into euros, applies the rules German tax law expects, and hands you a structured summary for your tax return. The figures are a starting point, not a verdict. For your personal situation, please review the result and ask a tax advisor (Steuerberater).
Is my data safe?
Yes. Your data never leaves your computer. Everything is calculated in your own browser, so there is no upload and no server copy. We have no technical way to see your transactions. When you close the page, the data is gone.
Which tax years are supported?
capi.tax covers tax years from 2018 through the current year. The rules that applied in each year are used for that year automatically, so an older return is calculated by the rules that were in force at the time.
Which brokers are supported?
Interactive Brokers and Tastytrade. You upload the transaction export from your broker as a CSV file, and capi.tax recognises the format. Support for further brokers is planned.
What does it cost?
capi.tax is currently free of charge. It is a private project — feedback is very welcome. There is no subscription and no account required.
How accurate is the FIFO calculation?
It follows German tax rules closely. Each security is tracked on its own, and every sale is matched to your oldest purchases first. The accuracy depends on giving capi.tax your full history for each investment — if a sale has no matching purchase in your file, it is flagged so you can add the missing purchase.
Why are some trades left out of my totals?
If a position was opened in a year earlier than the file you uploaded — for example options bought in 2024 that expired in 2025 — the closing trade has no matching purchase and cannot be calculated. Rather than guessing, capi.tax lists these as unmatched in the Audit trail tab and leaves them out of the totals. Re-export a date range that reaches back to when the position was opened, or declare the opening lot in the Adjustments tab, and the trade is counted again.
capi.tax prepares your data; it is not tax advice. Please review the figures and ask a tax advisor (Steuerberater) about your personal situation.