A plumber goes contracting and asks around. The agency says umbrella, because it is easiest for the agency. A mate says limited company, because it worked for him in 2019. A forum says sole trader, because someone on it once had a bad umbrella experience. All three answers were right for somebody. None of them was produced by looking at his situation, and his situation is the only input that matters.
What each structure trades away
An umbrella company employs you. Tax and National Insurance are handled through payroll, you get employment rights, and you carry almost no admin. In exchange you pay the umbrella's margin and give up most structuring choices. It suits short stints, first contracts, and anyone whose client insists the engagement is treated as employment for tax purposes.
Sole trade is the lightest self-employed structure: register with HMRC, keep records, file self assessment. Simple and cheap, but you and the business are legally the same person, which some agencies and end clients will not accept for contract work at all. That single fact eliminates the option for many contractors before tax enters the discussion.
A limited company separates you from the business, can be the most efficient wrapper at higher day rates, and creates real obligations: Companies House filings, corporation tax, payroll for yourself, and decisions about how to draw money out. It is a container that needs maintaining, and the maintenance is either your evenings or an accountant's fee.
Why the deciding factor is usually not tax
New contractors fixate on take-home percentage. The questions that decide the structure sit elsewhere. How does the off-payroll working regime treat this specific contract, and who decides that status? Will your agency deal with a sole trader at all? How long do you plan to contract, and is a mortgage application coming, since lenders read the three structures differently? What happens between contracts? These are questions about your life, and generic percentage tables know nothing about your life.
Bringing it to an accountant properly
This is one of the occasions where a single paid hour with an accountant beats a month of reading. Arrive with the facts they need: expected day rate, contract length, how the client views employment status, other income in the household, and your appetite for admin. Ask them to set out what you would take home under each structure and, more importantly, what each would demand from you through the year. General guidance can frame the options; only advice on your numbers can close the question.
Plenty of the 3,441 accounting firms listed on this site work with contractors as a core specialism, and their listings tend to say so. Look for that word when browsing firms near you, or describe your contracting setup and invite quotes for both the initial advice and the ongoing work.
Book the conversation before you sign the first contract, not after. Structures can be changed later, but unwinding the wrong one mid-year is where the real cost hides.
