Leaving the UK: the ten tax jobs that are cheap now and expensive later

Every autumn brings the same wave of new clients: people who left Britain over the summer, landed well, and are now discovering — one letter, one lightened rent statement, one locked login at a time — the admin they didn't know they were leaving behind. None of it is difficult. All of it is cheaper in the right order. This is the list we wish every leaver had six months before the flight.

Before you go

1. Set your UK day budget for the years ahead. The Statutory Residence Test decides how many UK days keep you non-resident — and for a leaver with family here and the house still available, the answer can be 45, not the 90 everyone assumes. Run the day-count checker before you promise anyone a monthly visit.
2. Rebalance property ownership between spouses, if one of you won't work abroad. Done before departure it's routine paperwork that can put most future rental profit inside an unused personal allowance — the difference between an annual bill and an annual nil. Done later, it's harder in every way.
3. Top up ISAs. Contributions stop the tax year you become non-resident; the wrapper itself keeps working. Use the allowance while you have it — and note some new countries (the US spectacularly) don't respect the wrapper at all.
4. If a company sale, share sale or crypto exit is on the horizon, sequence it now. The five-year temporary-non-residence rule drags gains realised abroad back onto your UK return if you come home within five years — and the difference between selling before departure, during, and after return can be the largest single number on this page.

Around departure

5. Tell HMRC your overseas address. Penalty notices go to your last known address — which is about to be your tenant's doormat. Two minutes online; prevents half the penalty-appeal letters we ever write.
6. Letting the house? NRL1 first. Before the first rent payment, or your agent is legally required to send 20% of the rent to HMRC (how that plays out).
7. Fix your Government Gateway. Move two-factor authentication off your UK mobile before the SIM dies, or your first January abroad features a locked account and a helpline that opens at 3am your time.
8. Tell the Student Loans Company if you have a loan — you're required to, the overseas repayment thresholds differ by country, and silence triggers default penalties on a schedule nobody reads.

After you land

9. File the departure-year return: split year, P85, refund. The year you leave usually splits into a UK part and an overseas part; PAYE on your final months routinely overshoots; the refund is typically four figures and does not claim itself. This return needs the SA109 pages HMRC's own website can't file — the plumbing guide explains the workaround options.
10. Start voluntary NI from day one abroad. Class 2 at £3.50 a week, applied for on the CF83 while the qualifying conditions are fresh — the best-value form in this entire list, and the one with a rolling annual expiry on back-years.

The pattern behind all ten

Every item is either free or nearly so in the window around departure, and every one has a failure mode measured in hundreds or thousands later: withheld rent, missed refunds, locked accounts, expired NI years, gains dragged home. The departure review (£249, credited against your first year's return with us) runs your dates through all ten in a single session — most usefully in the month before you fly, still valuable in the first year after.

The two most expensive items, ranked by what we see

If the full ten feel like too much homework for moving month, triage by cost of failure. The most expensive miss is item 4 — selling a company or a large asset position in the wrong year relative to your five-year clock. We have seen this single sequencing point swing outcomes by six figures; it dwarfs everything else on the list and it is the one that cannot be repaired afterwards. The second is item 2 — spousal ownership left at 50/50, which quietly costs an allowance-sized slice of tax every single year of the rental, compounding for as long as you're away; five years of not-fixing-it commonly totals £8,000–£12,000. Everything else on the list is hundreds, recoverable, or both. That's the honest hierarchy: two decisions worth real planning, eight pieces of admin worth an organised fortnight.