I'm a US citizen resident in the UK. I have the opportunity to do some contract work for a Spanish company that would earn a relatively small amount of money - a one-off payment of less than €1250. This would be foreign income, so if I accept the offer, then I'd have to pay UK self-assessment tax for the first time.
Given that it's a pretty small amount of money, that I don't have any idea how complex or how much of a pain it is to file Self-Assessment (I've only ever done PAYE so far), and that I'll be applying for a UK settlement visa in the future (so I definitely don't want to risk having any errors on my tax returns), I'm considering turning down the offer just to avoid the hassle and stress of worrying that I'm doing it wrong. But if paying self-assessment in this circumstance is extremely simple and straightforward, then maybe I'm overthinking it.
Is filing self-assessment in this circumstance enough of a pain that it's reasonable for someone who hates doing paperwork to just turn down the offer, or is it easier than I think it is? Would I have to pay all my taxes for the year via Self-Assessment, or could I pay my taxes from my regular UK job by PAYE as normal and only file Self-Assessment for the small amount of foreign income? Any suggestions appreciated.