Philipp Lammers

I’m Philipp — Economics, studied in Cologne and Amsterdam with a focus on Quantitative Finance. Markets, models and the question of how numbers really come about are my craft. Investing and software development are not just a job but a genuine passion.

Even so, German tax law for DEGIRO portfolios initially caught me off guard. Not because I don’t know the rules, but because the practical implementation — FIFO across multiple years, currency conversion, ETF Teilfreistellung — is simply enormously time-consuming.

It started with individual messages from friends: „Hey, you know your way around finance — do you know how I get my DEGIRO trades into my tax return?" I helped, explained the logic, sent links.

Then more people came. And I realised: this is not a niche problem. Hundreds of thousands of Germans invest with DEGIRO, eToro or Interactive Brokers — and they all have the same question at year-end. No automatic tax deduction, no tax certificate, no clear guidance.

I started solving the problem systematically. First as a spreadsheet for myself, then as a tool that works for others too. KAPitan is the result.

What bothered me about existing solutions: you put data in, get a number out — but you don’t know how it was calculated. That’s not an option for a tax return. You sign it with your name.

KAPitan shows you not just the result but every step: which trades ended up in which loss offset bucket, how the ETF Teilfreistellung was applied, which withholding tax is credited. You can trace and verify every number before entering it into your tax return.

Your data stays your data. The CSV is deleted immediately after calculation — we store your transactions only for the FIFO calculation — you can delete them at any time.