Start with how you want to work, not just what you'll pay

The legal structure you choose on day one shapes almost everything that follows: how much tax you hand over, how much of your own money is on the line if something goes wrong, how much paperwork lands on your desk each year, and how easy it is to bring in a partner, borrow money or sell up later. It is tempting to pick the simplest option and get trading, but a little time spent now can save you a painful restructuring later.

There is no universally "best" structure. There is only the one that fits your plans, your appetite for admin and the risks you are actually taking. Here is how the three main options compare in practice.

Sole trader: straightforward, but you carry the risk personally

As a sole trader you are the business. You register with HMRC, file a Self Assessment tax return each year, and pay income tax and National Insurance on your profits. There is no Companies House filing, no annual accounts to publish, and you can keep your accounts relatively simple.

It suits people testing an idea, running a low-risk service business, or working alone with modest turnover. But the flip side is unlimited liability. If the business owes money or a client makes a claim, your personal assets — savings, car, even your home in serious cases — are exposed. Your business name also cannot be the same as an existing trademark, and you cannot call yourself "Ltd".

It is worth thinking about how a sole trader setup looks to lenders and larger clients. Some corporate customers simply prefer to buy from a limited company, and mortgage lenders can view self-employed income with more scrutiny.

Partnership: shared effort, shared exposure

A conventional partnership is essentially two or more sole traders working together. Each partner is self-employed, files their own return, and shares profits according to your agreement. Crucially, in a general partnership, each partner can be held liable for the debts and mistakes of the others. That is a serious risk if you are going into business with someone whose judgement you cannot fully control.

If you take this route, do not rely on a handshake. A written partnership agreement should cover profit shares, decision-making, what happens if someone wants out, and how disputes get resolved. Without one, you fall back on default legal rules that may not suit either of you.

An alternative worth knowing about is the limited liability partnership (LLP). It gives you the flexibility of a partnership with the liability protection of a company, but it comes with Companies House filing obligations. LLPs tend to suit professional practices — solicitors, accountants, surveyors — more than typical small trading businesses.

Limited company: a separate legal person

Registering a limited company at Companies House creates a distinct legal entity. The company owns the business, signs the contracts and carries the debts. Your personal liability is generally capped at any unpaid shares you hold, which is the big attraction for anyone taking on staff, premises or significant contracts.

The trade-off is structure and disclosure. You will need to file annual accounts and a confirmation statement, both publicly visible. You pay corporation tax on profits rather than income tax. If you take money out, you usually do it through a combination of salary (subject to PAYE) and dividends, and the dividend allowance is now quite modest, so this needs proper planning rather than guesswork.

Most owner-managers end up weighing salary against dividends each year. The answer changes as your profits grow, so it is worth revisiting annually rather than setting it once and forgetting it.

The tax and admin questions that usually decide it

• Profit level. At low profits, sole trader is often simpler and no more expensive. As profits rise, the corporation tax and dividend route can become more efficient — but only once accountancy fees are factored in.
• VAT. You must register once your turnover passes the threshold, currently £90,000. This is separate from your legal structure, but it affects cash flow and pricing either way.
• Risk. If a client could sue you, you handle other people's property, or you are taking on debt, limited liability usually earns its keep.
• Who you work with. Contractors working through their own companies may fall inside off-payroll rules, which can make clients insist on how you engage.
• Growth and exit. Bringing in investors, issuing shares or selling the business is far easier through a company.

A practical checklist before you register

Before you commit, do four things. First, write down a realistic twelve-month profit forecast — not a hopeful one — and run the numbers through both a sole trader and a limited company scenario. Second, decide whether you are carrying any real liability, and whether you can insure against it instead of hiding behind a structure. Third, check the name you want is free at Companies House and not someone else's trademark. Fourth, speak to an accountant for an hour.

That last point is not a sales pitch. An accountant will tell you which expenses you can claim, how to set up PAYE if you need it, and whether your structure still fits in two years' time. You can always start as a sole trader and incorporate later — plenty of businesses do — but you cannot undo a personal liability once it has been incurred. Choose deliberately, and choose for the business you are actually building.