I just needed to figure out this one tax thing. Then one thing led to another.

By Jonas Maaløe

This all started innocently enough...

In 2023, after I’d returned to Copenhagen from living and working a few years in Berlin, I wanted to set up a simple private pension plan and needed to forecast my tax bill for the year.

Danish tax authorities actually makes this pretty straight forward by automatically calculating one for you based on your recent years’ tax data, so I looked up mine and learned that my tax forecast for the year was…a bunch of zeroes.

Which was technically correct—zero was indeed what I’d paid Danish tax authorities in recent years when I lived (and paid taxes) in Germany—but also not very helpful.

To understand pension plan contributions I’d essentially have to ‘First Principles’ my way through the Danish tax system.

Then I had a thought:

Tax laws are really just closed systems. Building a model to account for 80% of the important stuff

I mean—how hard could that be?”

Sigh…

Dear reader: After spending 1 1/2 months on it, I can confidentially say: Pretty hard. Which is why I’m happy to announce that I’ve made a whole interactive tax calculator for dummides which: