I would highly recommend asking an accountants advice, I assume there are similar services for when you file in the UK. Finding a CPA (Chartered Accountant in the UK) is huge, they’ll generally charge more but they can represent you in the event you get audited (had to look it up and confirm it’s the same for UK). Now if you get audited, they have a vested interest in protecting you. In the US they’re often legally obligated to protect you (and themselves).