Upload & processing

This page walks you through getting your broker file into capi.tax and explains what happens once it is loaded. The whole process takes a minute or two, and nothing you upload ever leaves your computer.

Before you start

You need one CSV file exported from your broker — currently Interactive Brokers or Tastytrade. The file should cover the trades for the tax year you want to prepare. The broker export pages in this help section show you where to find it.

Choosing the broker and tax year

Start by telling capi.tax two things:

• Which broker the file came from. This lets the tool read the columns correctly, since each broker uses its own layout.
• Which tax year you are preparing. The tool applies the rules that were in force for that year and only counts trades that belong to it.

If you pick the wrong broker, capi.tax usually notices and suggests the right one rather than producing odd results.

Dropping in your file

Once the broker and year are set, add your CSV. You can drag the file onto the upload area or click to pick it from your computer. The tool checks that it is a readable CSV; if you accidentally choose a PDF, a ZIP, or an empty file, you get a plain message explaining what went wrong so you can try again.

What happens next

Everything runs inside your browser. Your trades are never sent to a server, stored, or shared. capi.tax reads the file, matches your sales to earlier purchases using the FIFO method, converts every amount to euros using official Bundesbank rates, and works out the figures for your tax return. When it finishes, your results open automatically.

A note on incomplete history

Because sales are matched against your earlier purchases, the result depends on your full history with each investment. A common surprise: a position opened in a year earlier than your file — say options bought in 2024 that expired in 2025 — cannot be matched when you upload only the later year. capi.tax does not guess. It flags the closing trade as unmatched in the Audit trail tab and leaves it out of your totals until it is resolved, so nothing is counted on a false basis.

There are two ways to fix it:

• Upload one file that reaches back far enough. Re-export from your broker with a date range that starts when your oldest still-open position was opened, so every sale has its purchase in the same file.
• Declare the opening lot yourself. In the Adjustments tab, add the prior-year position as an Opening position (or Add purchase). Each adjustment is stored with a reason and the calculation is re-run.

Once the purchase is present, the trade flows back into your totals.

capi.tax prepares your data; it is not tax advice. Please review the figures and ask a tax advisor (Steuerberater) about your personal situation.