The UK and the US both tax the gain when you sell property — but they're not taxing the same number. The UK works in pounds, with its own reliefs and a fast 60-day deadline; the US works in dollars, with depreciation recapture, currency effects, and the Section 121 exclusion. Understanding where the two systems diverge is what lets you predict the real tax and use the foreign tax credit properly. This guide compares them side by side.
The short answer
Both countries tax property gains, but they measure and rate them differently — and the foreign tax credit reconciles them. The UK calculates the gain in pounds, applies reliefs like Private Residence Relief and the annual exempt amount, and requires reporting and payment within 60 days for residential property. The US calculates the gain in dollars (so exchange rates matter), requires depreciation recapture on former rentals, applies the Section 121 main-home exclusion, and reports on the annual return. For real estate the UK taxes first (situs rule); the US then taxes the same gain and credits the UK tax, so the UK liability is usually the floor.
Key takeaways
- The UK measures the gain in pounds; the US measures it in dollars (currency affects the US figure).
- The UK has a 60-day report-and-pay deadline for residential property; the US reports annually.
- The US adds depreciation recapture and the Section 121 cap; the UK has PRR and an annual exemption.
- For real estate, the UK taxes first; the US credits the UK tax via the foreign tax credit.
- Gaps arise where the UK charges nothing but the US still taxes gain above its cap.
Executive summary
The two systems share a goal — tax the gain on disposal — but reach different numbers through different mechanics. The UK computes a pound gain, subtracts its reliefs (Private Residence Relief on a main home, the annual exempt amount), and demands payment within 60 days for residential property. The US computes a dollar gain using exchange rates at purchase and sale, so currency movements can enlarge it; it then layers on depreciation recapture (for former rentals) and the Section 121 exclusion (for a main home, capped). The foreign tax credit is the bridge: because the UK taxes real estate first, the US credits that UK tax, usually leaving the UK liability as the effective floor. The interesting cases are the mismatches — where one system taxes and the other doesn't.
Same event, two different calculations
When you sell UK property, each country builds its own version of "the gain":
| Feature | UK CGT | US capital gains tax |
|---|---|---|
| Currency | Pounds | Dollars (rates at buy and sell) |
| Main-home relief | Private Residence Relief (can be full) | Section 121 (capped $250k/$500k) |
| Annual exemption | Annual exempt amount | None (separate from Section 121) |
| Depreciation recapture | No | Yes (former rentals, up to 25%) |
| Reporting deadline | 60 days (residential) | Annual return |
| Taxing order (real estate) | First (situs) | Second, credits UK tax |
The table shows why the two tax bills rarely match: different currency, different reliefs, and a US-only recapture charge.
Why currency alone can change the answer
This is the most counter-intuitive divergence. The US makes you translate purchase price and sale price into dollars at the exchange rate on each date. If the dollar strengthened during your ownership, the dollar-measured gain can be larger than the pound gain you actually felt — sometimes turning a modest pound profit into a bigger US gain. The UK, taxing in pounds, never sees this. (And note: this is separate from the Section 988 mortgage currency gain, which is about the loan, not the property.)
The 60-day rule and how it feeds the US credit
On the UK side, a resident disposing of UK residential property at a gain generally must report and pay within 60 days of completion — a tight, separate deadline from annual Self Assessment. For a US citizen, that's not just a UK chore: the UK tax you pay within 60 days becomes the foreign tax credit you later claim on your US annual return. So the sequence is usually: UK taxes first (within 60 days) → US return claims a credit for it. Getting the UK timing and figures right directly determines your US relief.
How the foreign tax credit reconciles them
Because real estate is taxed first by the country where it sits, the foreign tax credit lets you offset the UK CGT against the US tax on the same gain. Where UK tax is equal to or higher than the US tax (common, given UK rates), the credit can wipe out the US charge on the appreciation. Where it's lower or nil, US tax can remain. The two structural gaps:
- UK charges nothing, US still taxes: a main home fully covered by UK Private Residence Relief, but with gain above the US Section 121 cap — taxable in the US with no UK tax to credit.
- US measures more: currency effects or depreciation recapture create US gain the UK never taxed.
These gaps are where planning earns its keep — and where a generalist on either side tends to miss the cross-border picture.
Common mistakes we see
- Expecting the two tax bills to match — different currency and reliefs guarantee they won't.
- Ignoring currency, then being surprised by a larger US gain.
- Missing the UK 60-day deadline, which also complicates the US credit.
- Forgetting depreciation recapture is a US-only addition.
- Assuming the foreign tax credit always covers it — not when the UK charged nothing.
Related reading
- Selling a UK home as a US citizen — the main-home sale and the Section 121 cap.
- The Section 988 mortgage currency gain trap — the separate currency charge on the loan.
- UK property and US tax: the complete guide — the whole ownership journey.
This article is general information, not personalised advice. Because the UK and US compute property gains differently — in different currencies, with different reliefs — the only way to know your real combined tax is to model both. Book a free consultation and we'll calculate the UK and US position on your disposal and line up the foreign tax credit correctly.