Britain's 12% window is closing, and it won't reopen

The remittance basis is dead. It went on 6 April 2025, after roughly two centuries of letting UK residents park foreign income and gains offshore and pay nothing until they brought the money home. In its place sits the Foreign Income and Gains regime — four years of relief for new arrivals, then the full weight of the UK tax system on your worldwide income. That much has been chewed over.

What has been under-discussed is the exit ramp HMRC built for everyone caught by the change: the Temporary Repatriation Facility. It is the most generous transitional deal the Treasury has offered wealthy residents in a generation, and it is deliberately, explicitly temporary. The cheapest years are running out now. My view: if you sat on the remittance basis for a decade and you are still sitting on the fence, you are the person this piece is about.

What actually changed

Two things happened at once, and it is worth keeping them apart.

First, the going-forward regime. The remittance basis is gone. New residents — anyone arriving after ten consecutive non-resident years — get the FIG regime: four tax years in which foreign income and gains can be brought to the UK free of UK tax, provided they claim it correctly. After year four, you are taxed like any other UK resident, on your worldwide income, whether or not you remit it. There are no extensions and no discretionary top-ups. Four years, then the meter runs at full rate.

Second, the legacy problem. Long-term residents who used the remittance basis have, in many cases, decades of foreign income and gains sitting offshore — untaxed only so long as it never touches Britain. Under the old rules, remitting any of it triggered tax at ordinary rates, which is precisely why so much of it never came home. The abolition of the remittance basis did not erase that latent charge. It left a very large pool of money that is expensive to move and awkward to leave where it is.

The TRF is the bridge between the two.

How the Temporary Repatriation Facility works

The mechanism is elegant, and that is not a word I use lightly about tax policy. Former remittance-basis users can designate pre-6-April-2025 foreign income and gains and pay a reduced flat charge on the designated amount. Once designated, that money is decoupled from the old remittance rules entirely. You can bring it to the UK later — or move it, mix it, spend it — without the ordinary remittance charge biting again. You pay the flat rate once, on designation, and the money is clean.

The rate is the whole story, because it is on a timer:

Three tax years. Two of them at the lower rate, one at the higher, then nothing. After the window shuts, those same funds revert to ordinary treatment on remittance — which, for a higher-rate individual, means a charge several times the TRF figure. The gap between the flat designation rate and the ordinary rate is the entire prize. It is one of the widest deliberate arbitrages a tax authority has ever handed to its own residents, and it is closing on a published schedule.

Who is leaving it too late

The obvious mistake is procrastination — assuming three tax years is plenty of runway. It is not, for two reasons.

The lower rate covers only two of the three years. If you designate in 2027/28, you pay half again more than someone who moved in 2025/26 or 2026/27. The headline "12% window" is really a two-year window with a consolation year attached.

Designation is not a form you file in an afternoon. To designate intelligently you need to identify which offshore pools qualify, untangle mixed funds where income, gains and clean capital have commingled over years, and decide how much to designate against the rate you are prepared to pay. That is forensic work on old accounts, often across multiple jurisdictions and trustees. Advisers who do this properly are already booked. Leaving it to the final months of the lower-rate tier is how people end up designating in the 15% year by default, or missing the window altogether.

The second group leaving it too late are those conflating the TRF with the FIG regime. They are not substitutes. FIG governs income and gains arising now, in your first four UK years. TRF governs the legacy stock earned under the old remittance basis. A new arrival gets FIG; they have no TRF-eligible funds. A twenty-year resident gets no FIG at all — their four years are long gone — but may have an enormous TRF opportunity. Confusing the two leads people to think they have relief they do not have, or to ignore relief they urgently should use.

The uncomfortable part

Here is the uncomfortable part. The TRF is generous because the Treasury wants the money onshore and taxed once, cleanly, rather than sitting offshore forever generating nothing. That alignment of interests is real, but it cuts against the instinct that made remittance-basis planning work for so long: keep it offshore, keep it quiet, keep it untouched.

That instinct is now obsolete on two fronts. The remittance shelter is gone, so leaving money offshore no longer defers a UK charge — it merely postpones a reckoning at worse rates. And the wider transparency machinery — automatic exchange of financial account data, and from 2026 the crypto-asset reporting regime layered on top — means "offshore and quiet" is no longer a coherent strategy anyway. The information reaches HMRC regardless. The only variable left in your control is the rate at which you regularise, and the TRF is the cheapest rate you will ever see on this money.

Designation is irreversible and it is a real cash outlay today against a benefit you may realise years later. That is a genuine trade-off, not a free lunch, and for someone who never intends to bring a penny to the UK and plans to leave before it matters, doing nothing can be defensible. But that is a narrow case. For anyone who lives in Britain, intends to keep living in Britain, and has legacy offshore wealth they would eventually like to use, the maths is one-directional.

The verdict

The Temporary Repatriation Facility is the best deal the UK will offer wealthy long-term residents this decade, and it was designed to expire. The lower rate is live for 2025/26 and 2026/27; it steps up for 2027/28; then it is gone and ordinary remittance rates return.

If you used the remittance basis and hold significant pre-April-2025 offshore income and gains, treat this as a hard deadline, not a someday. The work of identifying and untangling qualifying funds takes months, the cheapest tier covers only two tax years, and the arbitrage between the flat designation rate and ordinary rates is too large to leave on the table through inertia. Confirm whether you have FIG relief, TRF eligibility, or both — they are different regimes for different money — and if the TRF applies to you, designate in a lower-rate year. This window will not reopen. Governments do not repeat one-off amnesties that worked.