Now first of all I live in spain and I'm wondering if someone has ever paid taxes with money acquired from signature campaigns here. I made a decent amount of money a year ago because campaigns were giving 0.03-0.04 per week. I wouldn't really know how to pay taxes if I need to, would this count like a job and how exactly would someone prove they got their bitcoins from signature campaign , seems quite difficult.
Edit
A few options are presented:
1. Don't say anything, it's virtually impossible for any tax agency to find out what you have. However eventually they might be able to and you could face serious problems.
2. Mark it as freelance work and a tax rate will be applied to it, up to 50% (reported by an user) It seems that they wont ask for much information or proof as long as you are declaring it intentionally.
3. Simply spend bitcoins or any other cryptocurrency that you earned without ever converting it to fiat because cryptocurrencies are usually not taxable in most European countries.
