You can register a limited company in the UK faster than you can eat a decent sandwich, and be trading the same afternoon. That ease is a real advantage. It is also why so many founders meet their first expensive mistake months later, usually in a brown envelope from HMRC or a polite letter from a client's solicitor. The errors below are not exotic. They are the same handful of things that trip up new owners again and again, and every one of them is cheaper to avoid now than to unpick later.
Choosing a business structure by accident
Most people do not really choose between a sole trader and a limited company. A friend recommends one, an accountant mentions the other, and the decision gets made by default. That is the wrong way round, because the structure affects your personal risk, your admin load and how you pay tax.
Sole trader
You and the business are the same legal entity. Setup is minimal, record-keeping is lighter, and you pay income tax and National Insurance through Self Assessment. The trade-off is that you are personally liable for business debts. If a client sues or a supplier goes unpaid, your personal assets are in the frame.
Limited company
A separate legal entity, which is why the liability is generally limited to what you have invested — with important exceptions around personal guarantees, fraud and wrongful trading. In exchange you take on statutory duties: annual accounts, a confirmation statement, Corporation Tax, and obligations as a director.
You can switch later, but it comes with tax consequences and a new set of filings. If you are genuinely unsure, spend an hour with an accountant before you register rather than after. It is the cheapest advice you will ever buy.
Registering with one body and forgetting the other
Companies House and HMRC are not the same organisation and do not talk to each other on your behalf. Incorporating a company tells Companies House you exist. It does not register you for Corporation Tax.
New companies need to tell HMRC they have started trading and register for Corporation Tax, generally within three months of doing so. Sole traders must register for Self Assessment by 5 October following the end of the tax year in which they started trading. Miss either and you are looking at penalties on top of the tax.
Beyond that, check whether you also need to register for VAT, set up PAYE if you are hiring, and notify the Information Commissioner's Office if you are processing personal data. Rules and thresholds change, so confirm the current position on GOV.UK rather than trusting a blog post from 2019 — including this one.
Treating the business bank account as optional
A separate account is not strictly a legal requirement for a sole trader, but it is close to essential in practice. For a limited company, the money in the account belongs to the company, not to you. Spending it on a holiday because it was sitting there is how directors end up with loans to the company, awkward tax questions and a filing headache.
Decide how you will take money out — salary, dividends, or drawings — and record which is which. Move a fixed percentage of every payment you receive into a separate tax pot the day it lands. Keep receipts, invoices and bank statements, because HMRC can ask to see them, and your accountant will charge you more to reconstruct a year of chaos than to file a tidy one.
Missing deadlines and underestimating the tax bill
Tax does not wait for a quiet week. The dates worth diarising now:
- 5 October — deadline to register for Self Assessment if you started self-employment in the previous tax year.
- 31 January — online Self Assessment return and balancing payment due, plus the first payment on account.
- 31 July — second payment on account.
- Corporation Tax — payment is normally due nine months and one day after the end of your accounting period; the return follows later.
- VAT — returns and payments are usually quarterly, due around a month and a week after the period ends.
- PAYE — monthly or quarterly, depending on your payroll size.
Payments on account catch out almost every first-year sole trader: you pay this year's bill and half of next year's in the same month. Budget for it in advance, or January will feel like a mugging.
Cash-flow mistakes that sink profitable businesses
Profit is an accounting figure. Cash is what pays wages, stock and rent. Plenty of businesses fail while showing a healthy profit, because the money is sitting in someone else's bank account.
- Invoice late, or not at all. Send the invoice the day the work is done, not at the end of the month when you remember.
- No written payment terms. "Payment within 30 days" needs to be agreed in writing, with a late-payment charge stated. Otherwise you are relying on goodwill.
- No deposit. For anything involving materials, custom work or a long project, take a deposit and stage the rest.
- One big client. If a single customer is more than half your revenue, you do not have a business, you have a job with extra risk.
- Spending before earning. New equipment, a van, a smart website — none of it is urgent enough to drain your buffer in month one.
- Confusing your money with the tax pot. HMRC is not a lender, and it does not offer generous terms.
Keep a rolling cash-flow forecast: money in, money out, week by week, for the next three months. It takes twenty minutes a week and it is the single best early-warning system you have.
Nobody ever regretted having three months of running costs in the bank. Plenty have regretted not having one.
Skipping the protective paperwork
A one-page agreement covering scope, price, payment terms, who owns the intellectual property, and how either side can end the arrangement will save you an enormous amount of grief. Clients who "just want to get started" are the ones most likely to dispute the invoice later.
Insurance matters too. Employers' liability cover is a legal requirement as soon as you take on staff, with limited exceptions, and your clients or contracts may require professional indemnity or public liability cover. Check whether you need a licence or permit from your local council or a sector regulator — food, alcohol, waste handling, childcare and financial services all have their own rules. On contracts, insurance and regulatory questions, a solicitor or broker is worth the fee.
What to do in your first week
None of this requires a consultant. Open a separate business bank account, register with HMRC and Companies House as applicable, diarise the deadlines above with reminders two weeks early, and set up a standing transfer of a set percentage into a tax savings account. Write down your payment terms, send your first invoice promptly, and book one session with an accountant who works with businesses your size.
Then get on with the part you actually enjoy. Good foundations are dull, invisible and the reason you are still trading in five years.
Photo: nehasharma01 / Pixabay
