In the US you have to give OF your tax info SS#, DL# and the ID has to have the current legal name attached to it. You also receive fill out OF earnings on 1040 form for filing so the IRS already knows, same for people in the UK under whatever system they have.
What people don't understand about Onlyfans is they take 20% as their cut then the creator is responsible for their own deductions which OF reports your earnings to the IRS. So thats up to another 30% taken from the gross amount earned depending on state taxes where you live. Basically whatever you think a creators gross income is they get 50-70% of that. Now if hoes are smart they see a real taxman and use everything imaginable as a deduction for filing, internet bill, phone bill, a bed, gas if they travel to shoot, hotel bill, fake receipts for expensive ass sex toys etc. Anything that can be justified as an expense that generated income from OF.