UK Capital Gains Tax for Cross-Border Taxpayers

What UK CGT covers

Capital gains tax applies when a UK resident disposes of a chargeable asset at a gain — shares, funds, property other than an exempt main residence, business interests, and more. Residence is the trigger: a UK resident is generally within CGT on worldwide disposals, while a non-resident is mostly outside UK CGT except for UK land and property (and certain property-rich interests).

Gains are reported through Self Assessment, except where the special property regime described below applies first. Rates depend on the asset type and your income level; check the current figures on GOV.UK rather than relying on remembered ones, as they have moved in recent years.

The annual exempt amount

Each individual has an annual exempt amount — a slice of gains each tax year that is free of CGT. It is currently £3,000 for individuals (and £1,500 for most trusts), a fraction of its former level, which has pulled far more ordinary investors into reporting than a few years ago.

Gains above the exemption are taxable; unused exemption does not carry forward. For US citizens the exemption illustrates the central cross-border problem neatly: the US has no equivalent, so a gain sitting comfortably inside the UK exemption is still fully taxable in the US — with no UK tax available to credit against it.

Selling UK residential property: the 60-day rule

Disposals of UK residential property have their own accelerated regime. Where CGT is due on the sale, a standalone online property return must be filed and a payment on account of the tax made within 60 days of completion. This is separate from the annual Self Assessment return, and the deadline arrives fast — often before sellers have even chosen an accountant.

Non-residents face a stricter version: a 60-day return for disposals of UK property is generally required even where no tax is due. Late returns attract penalties in their own right. If a sale is on the horizon, line up the numbers before completion, not after.

Main residence relief

The reason most UK homeowners never meet CGT is private residence relief: a property that has been your only or main residence throughout your ownership is typically fully exempt, with final-period and other adjustments where you were absent, let the property, or used part exclusively for business. Where you have more than one home, an election can determine which one carries the relief — a decision with real consequences for internationally mobile owners who keep a home in each country.

Two computations, two currencies

For a US person in the UK, every disposal is computed twice:

Because each country measures the gain in its own currency, exchange-rate movement between purchase and sale creates gains and losses that exist in one system only. The same disposal can be a loss in sterling and a gain in dollars. Which country credits which tax then depends on the asset's situs and the treaty — mechanical once set up correctly, expensive when improvised.

Practical sequence for a planned disposal

Before selling anything substantial, it is worth establishing: your residence position for the year (including any FIG claim); both countries' computations of the expected gain; whether the 60-day regime applies; and where the credit for each tax will land. Done in that order, most cross-border disposals hold no surprises. We run that analysis as a single piece of work covering both returns.