Building a Cross-Country Payroll API: The Weird Problems I Didn't Expect webdev #fintech #ai #javascript Last year, while trying to estimate the real take-home pay of a potential job abroad, I started building my own German payroll tax engine. At first it was a simple question: "What would actually be left from the salary after taxes and deductions?" But once the German calculation layer existed, adding other countries felt almost inevitable. So I expanded into Austria, Switzerland, the UK, Ireland, the US, Canada, and Australia — the goal being a unified API layer for cross-country salary comparison. The problem was that the deeper I went, the less universal the concept of "salary" actually became. The "same salary" illusion My initial assumption was that cross-country salary comparison was mostly a math problem: feed in a gross salary, apply taxes, compare the outputs. That assumption collapsed surprisingly quickly.…