The Founder's Guide to UK Company Formation and Structure

Most founders treat company formation as a paperwork exercise. They pick a structure that feels right, pay the registration fee, and move on to building the product. The decisions made in that first hour tend to be invisible until the company starts to scale, raise investment, or attempt to operate efficiently. Then they become visible all at once, often in the form of restructuring costs, blocked investment rounds, or tax bills that feel disproportionate to the activity that generated them.

The structural decisions worth thinking carefully about: which legal form you trade under, who controls the company at registration, how shares are allocated between co-founders, how vesting is structured, where the registered office sits, what the articles of association say about share rights, and how the founder agreements interact with the formal corporate documents. Each of these is reversible, but reversing each one costs time, money, and almost always a difficult conversation with someone who joined the cap table earlier.

The good news is that getting the formation right is not expensive. The hard part is knowing which of the dozens of decisions actually matter and which are noise. This guide separates the two.

The first structural choice is whether to trade as a sole trader or to incorporate a limited company. Sole traders are individuals who run a business in their own name. Limited companies are separate legal entities, owned by shareholders and operated by directors. The difference is much larger than it sounds.

Sole traders pay income tax on all profits at marginal rates that hit 40% above £50,270 and 45% above £125,140 in 2026. They pay Class 2 and Class 4 National Insurance. Their business assets and personal assets are legally the same thing. If the business is sued or owes a debt, personal property is exposed. There is no separate corporate tax return; profits are declared on a Self Assessment return.

Limited companies pay corporation tax on profits at 19% to 25% depending on profit level. Founders extract money via salary, dividends, or pension contributions, each with its own tax treatment. Shareholders are protected from company debts in most circumstances, with narrow exceptions. The company files its own accounts at Companies House and its own CT600 with HMRC.

For startups specifically, the limited company form is almost always correct. Investors require it for SEIS/EIS. R&D tax credits only apply to companies. EMI option schemes, the standard equity incentive structure for UK startup hires, are limited-company only. Sole-trader structures cannot access any of these reliefs and cannot accept equity investment at all. Even for a business that does not currently need investment or tax reliefs, the limited company form is so widely expected by suppliers, partners, and B2B customers that operating as a sole trader actively limits the kinds of contracts you can win.

Companies House registration is the formal legal act of incorporating the company. It costs £50 online and is typically completed within 24 hours. The form (IN01) asks for the company name, the registered office address, the directors, the persons with significant control (PSC), the share capital, and the articles of association. Each of these has long-term consequences and is worth thinking about carefully rather than picking defaults.

The company name has to be unique, must end in 'Limited' or 'Ltd', and cannot include sensitive words without permission. Beyond those rules, the choice is yours, but founders frequently regret picking names that are too generic, too similar to existing brands, or that pin them to a single product when the company will pivot. Check trademark availability and domain availability before submitting.

The registered office address is a public record. Anyone can look it up. For founders working from home, using the home address as the registered office is a privacy decision with consequences: spam mail, unsolicited service-providers, and occasional debt-recovery letters from unrelated companies that share the postcode. Most founders use a third-party registered office service for £30 to £100 per year.

Companies House registration creates the company. HMRC registration brings it into the tax system. The two are not the same and neither one is automatic from the other. Once incorporated, the company has to notify HMRC of its existence within three months of starting to trade, register for corporation tax, register for VAT if turnover requires it, and set up PAYE if it employs anyone (including the founder, where the founder takes a salary).

Most of these registrations are straightforward online via the company's HMRC business tax account. The error pattern that costs founders most is failing to register for one of them on time, incurring late notification penalties, or missing the VAT registration threshold and accidentally trading above it. The threshold has stayed at £90,000 (over a rolling 12-month period) since 2024 and the penalty for failing to register on time is calculated as a percentage of the VAT that should have been collected during the unregistered period.

For technology and SaaS startups specifically, the VAT position is worth getting right from the start. Place-of-supply rules for digital services sold internationally can make registration mandatory at lower turnover thresholds, depending on customer geography and product type.

The articles of association are the formal corporate constitution. They describe how shares are issued, how directors are appointed, how meetings are run, and what happens if a shareholder wants to sell. The shareholders' agreement is a separate document, signed by the shareholders, that covers the things the articles do not: vesting, founder commitments, anti-dilution rights, exit provisions, drag-along rights, and the specific conduct expected of co-founders.

Two of the most important provisions in a startup shareholders' agreement: vesting and good-leaver/bad-leaver clauses. Vesting means that founders' shares are not fully owned at incorporation but become owned (vest) over time, typically four years with a one-year cliff. If a founder leaves before vesting completes, the unvested shares revert to the company. This protects the company from a founder walking away on day 30 with 50% of the equity. Good-leaver/bad-leaver clauses define what happens to vested shares depending on whether the departure was amicable or not.

Without these provisions, a startup is exposed to one of the most common founder-failure modes: a co-founder leaves early, retains a substantial slice of equity, and either blocks future investment rounds or extracts disproportionate value at exit. Standard investor terms presume vesting; without it, your first term sheet will require restructuring.

Every UK company must have a registered office where official correspondence is sent. The address is on the public Companies House register. Anyone, anywhere, can search by company name and pull up the founder's address if the founder used their home address at incorporation. This is a meaningful privacy issue for founders who work from home or share a home with family.

Three options solve it. The first is to use a registered office service offered by formation agents and accountants. Costs £30 to £100 per year. Mail is forwarded or scanned to the founder. The second is to rent a serviced office or co-working space that includes a registered address. More expensive but useful when you need a real meeting space too. The third is to use the accountant's office, which is the cheapest where the accountant offers it as a bundled service.

Beyond privacy, the registered office address signals credibility. A central London or major-city address looks more substantial than a suburban residential street, particularly for B2B sales or investment outreach. The additional cost over a home address is small enough that most early-stage startups choose to upgrade.

Directors are the people legally responsible for running the company. The Companies Act 2006 sets out specific duties: act within powers, promote the success of the company, exercise independent judgement, exercise reasonable care and skill, avoid conflicts of interest, not accept benefits from third parties, and declare any interest in proposed transactions. These are not aspirational; they are legally enforceable obligations.

Most startups appoint the founders as directors at incorporation. That is correct, but it carries duties that founders sometimes underestimate. A director can be personally liable for company debts in specific circumstances: where the company traded while insolvent, where there has been wrongful trading, where personal guarantees were given on company loans, or where there is evidence of fraudulent preference between creditors. Limited liability protects directors in the routine case but is not absolute.

Directors are also personally responsible for filing accurate accounts at Companies House and submitting CT600 returns to HMRC on time. Late filing penalties at Companies House range from £150 to £1,500 for private companies, doubling for repeat offences. HMRC penalties for late CT600s start at £100 and escalate to 10% of unpaid tax at six months. These are corporate fines, but the underlying decisions sit with directors.

How shares are allocated at and shortly after incorporation determines the cap table for the rest of the company's life. Mistakes are reversible but expensive. The two patterns that recur most often: founders splitting equally without a vesting agreement, and founders giving early advisors or contractors equity without proper share-class structuring.

For co-founder splits, the headline question (50/50, 60/40, or other) matters less than people assume. What matters more is that all founders are vesting on the same terms, the dates are documented, and the agreement covers what happens if someone leaves or has to be removed. A 60/40 split with proper vesting is structurally sounder than a 50/50 split without.

For advisors and early employees, share allocations should typically come from a separate option pool rather than direct share issues. The standard structure is an EMI (Enterprise Management Incentive) option scheme, which provides material tax benefits to recipients and protects the cap table from being cluttered with small holdings. A 10% to 15% pool for the first 10 to 15 hires is standard. We cover EMI schemes in depth in Hub 6 (Attracting Talent).

If you are forming a startup and want to do it correctly, the right sequence is roughly: agree co-founder roles and equity split with vesting, draft the shareholders' agreement, choose a registered office, pick the company name and check trademark availability, incorporate at Companies House with bespoke articles where investment is on the horizon, register for corporation tax with HMRC, register for VAT if applicable, set up PAYE if the founders are taking salary, and open a business bank account.

Most of this can be done in a single week with a good accountant. The accountant fee for a clean formation is £500 to £1,500 depending on complexity. Founders who have done it before sometimes manage formation themselves; first-time founders almost always benefit from professional help, mostly because the failure modes are not visible until they bite.

Read each of the spokes below for the specific decision you are working through. The deeper the decision, the more value there is in the detail.