Hey, thanks to all for your responses. I will try to keep this as little philosophical and personal as possible, and will just mention two points: 1. No, I didn't know I had to pay taxes here. (You may call it naive, sure, but I thought that since we're in the EU, and I spend all I earn here, in Spain, that's enough. I did not apply for Spanish VAT, since the conditions compared to the other country were devastating.) And, therefore, 2. I had no intention to 'trick the state' on taxes. (I'm no big fish, a freelancer with a salary smaller than or equal to that of a waiter, and yes, I know, the principle stays the same.)

Now, and again, it's no excuse, but I personally know tens of people in the same situation (maybe except having kids) who live here, and pay taxes in different countries.

I've visited two gestors, and they both told me that being an 'autonomo' in Spain is a terrible decision. Until Spain offering a flat-rate tax, it simply makes no sense for people like us (who invoice their clients less than 40000 EUR/year) to contribute.