First: the two-account rule
Before HMRC, before business cards, before the website: open a separate account for the business money (a free Mettle account takes minutes) and decide your set-aside rate — the fixed percentage of every payment that goes into a tax pot on arrival. For most new freelancers, 20–25% is right. Do this from payment one and you'll never join the January-panic community; skip it and almost nothing else on this list will save you.
Why so blunt? Because self-employment's only real financial trap is that tax arrives late: you can trade for up to 21 months before the first bill lands — and when it does, payments on account can make it 150% of what you'd guessed. People who set aside from day one simply never experience the trap.
The full checklist covers registration and deadlines, the insurance and pension decisions, pricing your work, and the first-year traps that catch almost everyone else.
The official bit (10 minutes)
- Register for Self Assessment with HMRC as self-employed — deadline is 5 October after the end of your first tax year, but do it early; you'll need the UTR anyway.
- Check what you're leaving behind: workplace pension (it stays yours — note where it is), any share schemes, and your P45 for the return that covers your mixed year.
- Name: trade under your own name or a business name — no registration required, just avoid protected words and check trademarks/domains.
The money habits (the actual difference-makers)
- The tax pot — covered above. 20–25% of every receipt, automatically.
- A payday, not a raid. Pay yourself a fixed monthly amount from the business account to personal. It smooths feast-and-famine months, makes affordability decisions honest, and keeps the business account meaning something.
- Capture-at-source records. Receipts snapped the moment they exist, bank feed into FreeAgent (included free in our packages), fifteen minutes of review a week. This also quietly satisfies Making Tax Digital whenever your income brings you into scope.
The safety net (build it before you need it)
- Insurance: professional indemnity if you advise or create for clients (often contractually required), public liability if you're physically around people or property. Both are cheap relative to what they cover — and deductible.
- Pension: nobody auto-enrols you now. A SIPP or personal pension with a modest automatic monthly amount beats a perfect plan you never start — and contributions attract tax relief that gets more valuable as you earn more.
- Income buffer: aim for three months of personal costs in reserve. It's the difference between choosing clients and taking anything.
- Sick pay doesn't exist anymore: factor that into pricing (below), and consider income protection once your income justifies it.
Pricing your work (the 10-second formula)
Take the salary you'd want employed, add ~30% for the employer costs you now carry (pension, kit, insurance, software, holidays, sick days), then divide by realistic billable days — about 180/year, not 260. On £40k-equivalent: £40k × 1.3 ÷ 180 ≈ £290/day minimum. Most new freelancers price off their old daily salary and accidentally take a 40% pay cut. Don't.
First-year traps, named
- Spending the VAT-threshold question too late — watch rolling turnover from month one if you're consumer-facing.
- Assuming "no tax bill yet" means "no tax owed yet".
- Under-claiming expenses out of nervousness — see our expenses guide; claiming what's legitimate isn't cheeky, it's the system.
- Working without a written scope — scope creep is unpaid work you volunteered for.
- Doing all of this alone when £19 + VAT a month buys a named accountant, the software and the return. That's us.
