I'm a Finnish (FI) citizen working with a full-time contract in a company. I'm going to do a 3 months job abroad in Belgium (BE) in a different company. During this time my contract in FI is going to be suspended, and therefore I only have income from BE. I'm confused on whether and where I should pay income tax for that three months time.
From the top of my head this situation looks like this:
- Finnish tax agency point of view: I have income worth of only 9 months for the whole year, which results in a tax refund since my annual income was less than expected.
- Belgian tax agency point of view: I have income worth of only 3 months for the whole year, which is significantly less than the calculated annual income and thus I get withheld tax refunded.
This doesn't seem right. To avoid any financial surprises I'd like to know what would be the correct way to deal with this, e.g. which country should the tax money go to and how do I make it go that way? I read that many countries have double tax agreements, which spare taxpayers from double taxation. This of course implies that both countries are aware of the income. Does this happen automatically or do I have to explicitly claim my income from BE as income in FI?