what do you tell an emplyer that youve done a job to explain a gap in your cv? you cant say you are a sex worker? what do you say?

Looking after ill / disabled/ dying relative or friend, travelling abroad, self employed dog walker/ reiki therapist / home sitter etc or any vague self employable skill unrelated to the job you're applying for 

Personal assistant/secretary (insert business owner friend or client willing to use their name as reference), nanny, self employed cleaner, online admin/data job, phone answering service for lawyer,/doctor,/therapist (insert friend willing to use their name as reference)

what do you tell an emplyer that youve done a job to explain a gap in your cv? you cant say you are a sex worker? what do you say?

Hard to answer this without other info; how long is the gap, what other kinds of work have you done in the past, any qualifications or volunteering you could 'duplicate' etc etc

If you’re paying tax then there will not be a gap ? Just self employed

How and why would a prospective employer look into the OP's tax affairs? Unless it's a job with HMRC (and even then they'd be on pretty thin ice if they started poking about without her say so).

you cant say you are a sex worker? what do you say?

You can say you're a sex worker, you just don't want to which is fine. I would avoid making up jobs (as you're likely to be found out) and go with either the travel (provided you can back it up in the event you run into somebody who knows the place you're claiming to have been in) or some caring responsibilities which are going to be very hard to disprove