Leaving My Job to Start a Building Business: Checklist
The short answer
Don't hand in your notice until four things are true: you have months of personal bills saved, your first paid jobs are lined up, your paperwork is ready, and you have a tax pot rule. Then the leap is a plan, not a jump.
- Save a runway first. Work out your monthly personal bills and save several months before you leave.
- Line up 2–3 paid jobs before you resign. Start with people who already know your work.
- Plan for the January bill. Your first tax bill can include half of next year's tax on top.
- Your first 90 days are about selling. Calls, visits and quotes every week, not a logo or a van wrap.
Written by Sviat Jay, founder of BizMentor and of Craftex, a London design & build company. Tax figures use the 2026 to 2027 rates published on gov.uk for a sole trader in England. Check your own position with an accountant.
Thinking about leaving your job to start a building business? I came to the UK with £6K of debt, started as a demolition labourer, then worked as a carpenter. Within three years my company turned over £1M a year.
Below is the checklist to run before you hand in your notice. To talk your plan through, book a free strategy call.
Leaving your job to start a building business: the 4 tests
Hand in your notice when you can say yes to all four:
- Runway You have several months of personal bills saved.
- Work Two or three paid jobs are booked for your first month.
- Paperwork Registration, insurance and a business bank account are ready.
- Tax pot You know what share of every payment goes into a separate account.
Miss one and the leap gets risky. Miss two and keep the job a little longer. Build the business in evenings and weekends until the gaps close.
Starting while employed is a sensible way in. Quote small jobs at weekends, learn to price and collect reviews. When weekend work pays more than overtime would, you're close. Still deciding? Run the numbers in is it worth starting a construction company.
Work out your runway before you resign
Your runway is how many months you can pay your own bills with no income. In the first months, jobs come late and payments come later.
Add up your personal bills: rent or mortgage, food, car, phone, family costs. Then:
| Monthly bills | 3 months | 6 months |
|---|---|---|
| £1,500 | £4,500 | £9,000 |
| £2,000 | £6,000 | £12,000 |
| £2,500 | £7,500 | £15,000 |
Example figures only. Use your own. Keep this money apart from the business. It's for your family, not for tools or materials. If you have little or nothing saved, read how to start a construction company with no money first.
Ready to leave, but not sure where the first jobs will come from?
Book a free call with our team. We'll look at your trade, your contacts and your savings, and plan your first 90 days.
Line up your first paid jobs before you leave
The fastest work comes from people who already know you. Before you resign, make a list and start calling:
- Past clients you've done private work for.
- Former employers and site managers who need a reliable pair of hands.
- Colleagues who've already gone self-employed and turn work away.
- Suppliers and merchants who know which builders are busy.
Aim for 300 calls over your first weeks. Tell people you now take on full jobs and offer a referral fee. Read your employment contract first: check your notice period and any clause about working for your employer's clients.
Oleg made the same move at 19. He went from £100 a day on London sites to his own company and his own clients.
Oleg: from £100 a day on site to £7K a month profit in 2 months
A 19-year-old taper and jointer who started his own company and built a team of 10+. Individual results, not typical or guaranteed.
Get the paperwork ready in week one
None of this is hard, but do it before the first invoice:
- Register as self-employed. Tell HMRC by 5 October after the end of the tax year you started in. Late registration can bring a penalty.
- Register for CIS if you'll work for contractors. Registered, they deduct 20% from your labour. Not registered, they deduct 30%.
- Insurance. Public liability before you set foot on a client's site, and cover for your tools and van.
- A separate bank account. Every job paid in, every cost paid out. Nothing mixed with personal spending.
- Sole trader or limited company. Sole trader is the simplest start. Our step-by-step guide to starting a construction company covers the choice.
Not sure your first jobs will be there when the wage stops?
Book a free call and we'll plan your first 90 days with you.
The first-year tax bill nobody warns you about
On a wage, tax leaves before you see it. Self-employed, you pay it later, in one go. And the first bill is bigger than you expect, because of payments on account.
HMRC asks you to pay towards next year's tax in advance. Each payment is half of your last bill, due on 31 January and 31 July. You don't make them if your last bill was under £1,000, or if over 80% of your tax was already paid.
Worked example (sole trader in England, 2026 to 2027 rates, no other income):
| Item | Amount |
|---|---|
| Profit for the year | £40,000 |
| Income Tax: 20% above £12,570 | £5,486 |
| Class 4 National Insurance: 6% above £12,570 | £1,646 |
| Tax for the year | £7,132 |
| Plus first payment on account (half) | £3,566 |
| Due on 31 January | £10,698 |
That's the shock. £7,132 is about 18% of profit, but the January bill is over a quarter of it.
Our rule: move 25% of every payment into a tax account the day it lands. CIS deductions count towards the bill, so working for contractors lowers what you owe in January.
Spending the CIS refund or the tax pot on a new van in year one. The bill in January always arrives. The van can wait.
Your first 90 days on your own
The first 90 days decide whether you go back to a wage. Spend them on sales, not on looks:
- Weeks 1–4 Call your list, visit every lead within days, quote every job properly.
- Weeks 5–8 Follow up every quote, ask every client for a review and a referral.
- Weeks 9–12 Look at your numbers: jobs won, profit per job, money in the tax pot.
Skip the logo, the van wrap and paid ads for now. If the phone goes quiet, our 30-day plan for a new company with no work shows what to do next. Want help with yours? Book a free strategy call, or see how our programs for new building companies work.
Where is your new business weakest? Take the free 4-minute Construction Business Scorecard: 18 questions on your pipeline, sales, pricing, cash flow and systems, with your weakest area shown first.
Scared to start? Turn the fear into numbers
Fear is normal. I started as a labourer with £6K of debt. The fear is usually about three things: no money, no work and the tax bill. Each one has a number:
- Money Your runway in months.
- Work The jobs booked for month one.
- Tax 25% of every payment in a separate account.
Write those three numbers down. If they look weak, you don't need courage. You need more time in the job and a better plan.
That's where mentoring helps most. I run Craftex today and work with owners one-to-one; owners just starting out join a small group with regular one-to-one time. Every program is built for results in about 4 months, not years. Individual results, not typical or guaranteed.
20+ Ways to Get Construction Projects in the UK
Every channel we use at Craftex to find work, with scripts and a 30-day plan.
Get the free guideBefore you hand in your notice
Tax rates and thresholds change every April. Check gov.uk or your accountant before you rely on the figures above.
Before you go
- You know your monthly personal bills and have months of them saved
- Two or three paid jobs are booked for month one
- You've read your employment contract and know your notice period
- Self-employment, CIS, insurance and a bank account are ready
- 25% of every payment goes into a tax account from day one
