Most UK founders should start as a sole trader and incorporate when profits exceed roughly £30,000-£40,000. Below that, the tax saving from a limited company rarely outweighs the extra administration. Above that, limited liability and Corporation Tax efficiency start to pay back the work.

This is the standard rule of thumb. The decision turns on three things: tax efficiency, personal liability, and operational complexity. Run all three through your own numbers before deciding.

How they differ

A sole trader is an individual running a business in their own name. There''s no separate legal entity — you and the business are the same person for liability and tax purposes. Setup is essentially free; you just register for Self Assessment with HMRC.

A limited company is a separate legal entity, incorporated at Companies House. The company''s debts are its own — shareholders'' personal assets are protected (with narrow exceptions for fraud or wrongful trading). The company pays Corporation Tax on profits; shareholders pay personal tax on what they extract as salary or dividends.

Tax efficiency

Sole traders pay Income Tax (20% / 40% / 45%) plus Class 4 National Insurance (typically 6% / 2%) on profits, with the personal allowance and basic-rate band shared with any other income they have.

Limited companies pay Corporation Tax — 19% on profits up to £50,000, 25% on profits over £250,000, with marginal relief tapering between the two for accounting periods in 2026. Profits extracted as dividends incur a personal tax charge on top, but the dividend rates (8.75% / 33.75% / 39.35%) and the £500 annual dividend allowance generally still produce a lower combined tax bill than sole trader treatment once profits cross ~£30,000-£40,000.

The exact tipping point depends on your other income, pension contributions, and whether you reinvest profits in the business or extract them. A two-year tax projection from a qualified accountant is usually worth its fee.

Personal liability

Sole traders carry unlimited personal liability. If the business owes a supplier £20,000 and can''t pay, the supplier can pursue you personally — your savings, your home, anything you own.

Limited company shareholders have liability limited to the unpaid amount on their shares (typically £1 in a one-person company). The company''s creditors can pursue the company; they can''t come for the shareholder''s personal assets unless the shareholder personally guaranteed the debt (which lenders often require for small companies — read your bank''s loan terms carefully).

This protection is the single biggest reason any business with meaningful debt, contractual liability, or operating risk should consider incorporation.

Operational complexity

A sole trader has one annual filing: Self Assessment by 31 January following the tax year end. Records can be kept on a spreadsheet if turnover is modest.

A limited company has more:

• Annual accounts to Companies House (publicly filed, 9 months after the period end).
• A confirmation statement to Companies House annually.
• A Corporation Tax return (CT600) to HMRC, 12 months after the period end.
• The director''s personal Self Assessment.
• PAYE filings if anyone (including the director) is on payroll.
• PSC register maintenance.

None of this is hard. It is more work — typically £80-£200/month for an accountant to handle, versus £30-£80/month for a sole trader.

The practical tipping point

Use this as a starting framework, not a rule:

• Profits under £30,000 and low operational risk: stay as a sole trader. The tax saving doesn''t justify the admin.
• Profits £30,000-£50,000: it depends. Run the numbers for your specific situation — if you''re extracting all profits as personal income, incorporation might not save much. If you''re reinvesting, the deferral matters.
• Profits over £50,000, or material liability exposure, or planning to raise investment: incorporate. The combination of tax efficiency, limited liability, and the ability to issue shares to investors or employees usually outweighs the extra administration.

What to do next

If you''re below the threshold and unsure: stay a sole trader for now and revisit at the next financial year-end. Incorporation isn''t a one-way door — you can move to a limited company later, transferring the trade across.

If you''re above the threshold: get a two-year tax projection from an accountant comparing the two structures with your specific income mix, then incorporate at the next sensible point in the financial year.