I work legally with a contract for 15 hours per week in a bar here in Spain and am a Resident. I have been told by my boss today that I will be liable for a tax bill in excess of 1,500 Euros shortly yet I do not know why this is. I have been working there for nearly two years on contract, yet this is the first time I have been told I need to pay this amount of money.

Can anyone tell me why?