More than 80 treaties decide who gets to tax wages, dividends and royalties that cross a border. How they work, and why you still have to claim them.

The fixation decides when your rate is next up for renegotiation. The end of the period matters more than most borrowers expect.

The same flat can carry a different tax bill in Prague and in a village outside it. The gap is a chain of multipliers, and the town controls two of them.