Before you start

A National Insurance number
PAYE registration through your employer
A Government Gateway account, if you ever need Self Assessment
Records of foreign income, overseas accounts and days spent outside the UK

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. Three bands where Scotland has six, and a materially later Higher rate threshold. The thresholds have been frozen for several years, which quietly pulls more people into higher bands each year as wages rise.
OnlineWho: You
3
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The personal allowance is withdrawn by £1 for every £2 earned above £100,000, giving an effective marginal rate of about 60% between £100,000 and £125,140. Pension salary sacrifice is the standard response. It is the most consequential quirk in the English system and it is signposted nowhere.
OnlineWho: You
4
If you work at sea, look at the Seafarers' Earnings Deduction before your first return
Seafarers who spend a qualifying period largely outside the UK working on a ship may claim 100% deduction against their earnings. It is a real and substantial relief, it depends on keeping meticulous records of days and voyages from day one, and it is easy to lose by failing to document rather than by failing to qualify. In a cruise and shipping city this catches more people than anywhere else in England.
OnlineWho: YouFrom your first voyage
5
Check whether you actually need to file Self Assessment
Most employees never do — PAYE handles it. You must register if you are self-employed, have significant untaxed income, or meet one of HMRC's listed triggers. Online returns are due by 31 January following the 5 April year end.
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
A record of days at sea and outside the UK, if you work on ships
Government Gateway credentials, for Self Assessment

Things most newcomers don’t know

The Seafarers' Earnings Deduction is the local tax fact, and it is won or lost on record-keeping.

Britain's cruise and merchant fleet is crewed and administered heavily from Southampton, and a qualifying seafarer can deduct 100% of their earnings from UK income tax. The qualifying period test is unforgiving and depends on documentary evidence of every voyage and every day. People discover the relief in year three and cannot substantiate years one and two.

Source: GOV.UK — Seafarers' Earnings Deduction

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. A rise from £99,000 to £110,000 delivers far less than it looks like. Model it before accepting an offer in that range, and look at salary sacrifice.

Source: GOV.UK — income tax rates and personal allowances

Frozen thresholds are a tax rise nobody voted for.

The personal allowance and the higher-rate threshold have been held flat for several years while wages rose, so each year more people cross into higher bands without any rate changing. The mechanism is called fiscal drag, and it is why your take-home percentage slips slightly each April even without a promotion.

Source: HMRC

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

Not checking the PAYE code on the first payslip, especially for a stray Scottish S or Welsh C prefix.
Working at sea without keeping a day-by-day record for a Seafarers' Earnings Deduction claim.
Accepting a salary between £100,000 and £125,140 without modelling the 60% effective band.
Counting the tax year as January to December rather than 6 April to 5 April.
Ignoring National Insurance when estimating take-home pay.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.

Make it your personal checklist

Globe Quest turns this into a tracked, AI-personalized plan for Southampton — timed to your move date, with reminders so nothing slips. Free to start.