Before you start
- A National Insurance number
- PAYE registration through your employer, or Self Assessment registration if you contract
- A Government Gateway account
- Records of foreign income and overseas accounts
Step-by-step
- 1
Check the tax code on your first payslip
PAYE deducts at source, so a wrong code means wrong deductions for months before anyone notices. Your code should not begin with an S — that is the Scottish prefix — or a C, which is the Welsh one. Both get applied in error by payroll teams run from elsewhere.
Via employerWho: YouFirst payslip - 2
Learn the three English bands
A personal allowance, then Basic, Higher from £50,270 and Additional from £125,140. The thresholds have been frozen for several years, which quietly pulls more people into higher bands each year as wages rise.
OnlineWho: You - 3
If a role is a contract, establish its IR35 status in writing before you accept
Under the off-payroll working rules the client — not you — decides whether an engagement is inside or outside IR35, and must give you a Status Determination Statement with reasons. Inside means income tax and National Insurance are deducted like employment despite the day rate; outside means you are taxed as a business. The gross rate tells you almost nothing until you know which. In a market as contractor-heavy as this one, ask for the determination at offer stage, not after.
Via employerWho: YouBefore accepting - 4
Understand the 60% trap above £100,000
The personal allowance is withdrawn by £1 for every £2 earned above £100,000, giving an effective marginal rate of about 60% between £100,000 and £125,140. Thames Valley technology salaries land people in this band routinely. Pension salary sacrifice is the standard response, and most of the large employers here offer it.
Via employerWho: You - 5
If you file, understand payments on account
In the January after your first profitable self-employed year you settle that year's tax and simultaneously pay the first instalment toward the next — commonly about 150% of a normal year's bill at once, with the second following in July. Set money aside from every invoice from day one, in a separate account rather than as a mental note.
OnlineWho: You - 6
Settle your residence position in year one
The Statutory Residence Test determines UK tax residence from days present and connecting factors. The UK abolished the old non-domiciled regime and replaced it with a residence-based system, and the transitional rules are genuinely complex. Take advice in the first year if you have foreign income or assets.
In personWho: You
Documents you’ll need
- National Insurance number
- P60 — the annual summary from your employer
- P45, if you change employer during the year
- Status Determination Statements for any contract engagements
- Government Gateway credentials, for Self Assessment
Things most newcomers don’t know
In the Thames Valley, a day rate means nothing until you know its IR35 status.
This is one of the densest contractor markets in Britain, and the off-payroll rules put the status decision on the end client, who must issue a Status Determination Statement. An inside-IR35 engagement is taxed essentially like employment without the employment rights; an outside one is not. Two contracts at the same headline rate can differ by a very large margin in take-home, and a newcomer with no UK tax history is the least equipped person in the room to notice. Ask for the determination before you sign.
Source: GOV.UK — understanding off-payroll working (IR35)
The 60% band between £100,000 and £125,140 is the biggest hidden rate in the system.
The personal allowance is withdrawn at £1 for every £2 above £100,000, so each extra pound in that range is taxed at the 40% headline rate plus the lost allowance — around 60% in effect. Thames Valley technology salaries put people into it routinely, and a rise from £99,000 to £110,000 delivers far less than it looks like. Model it before accepting, and look at salary sacrifice.
Source: GOV.UK — income tax rates and personal allowances
A Reading salary and a Reading rent is a better trade than a London salary and a Reading rent.
Income tax and National Insurance are identical wherever you live in England, so the arithmetic is rent plus commuting cost against salary. An annual season ticket to Paddington is a four-figure sum revised every March, before Underground travel at the other end, and Reading rents already run above the South East average. The town's real advantage is that it has senior, well-paid jobs of its own — take one and the commute line disappears entirely.
Source: community-reported
The tax year runs 6 April to 5 April, which catches everyone once.
Almost no other country uses these dates. It decides which year your arrival income falls into, when your P60 arrives, and when Self Assessment is due. Newcomers routinely reckon against a calendar year and get their first filing wrong.
Source: HMRC
Common mistakes to avoid
- Accepting a contract day rate without seeing the Status Determination Statement.
- Not checking the PAYE code on the first payslip, especially for a stray Scottish S or Welsh C prefix.
- Accepting a salary between £100,000 and £125,140 without modelling the 60% effective band.
- Comparing a Reading rent to a London rent without pricing the season ticket.
- Counting the tax year as January to December rather than 6 April to 5 April.
Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.
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Sources
- GOV.UK — Income Tax rates and Personal Allowances — official
- GOV.UK — understanding off-payroll working (IR35) — official
- GOV.UK — Self Assessment tax returns — official
- GOV.UK — understand your Self Assessment tax bill (payments on account) — official
- GOV.UK — tax on foreign income and residence — official
Last verified August 2026. Government processes change — always confirm critical details against the official source before acting.