Capital Gains on a UK Property Sale as a French Resident: How It Actually Works (2026)

• Selling UK property as a French tax resident means paying UK Capital Gains Tax first, under HMRC's own rules — the French 22/30-year holding-period allowance used for French property sales doesn't apply here at all
• Genuine acquisition, improvement, and selling costs reduce the UK gain before the 18%/24% rate applies — but unlike the French flat-rate options, HMRC requires actual costs, not a percentage shortcut
• You then declare the same gain in France, where a tax treaty credit offsets the UK tax you paid against your French income tax — but French social charges are calculated separately and aren't fully covered by that credit
• Proving you're affiliated with UK rather than French social security exempts the CSG/CRDS portion of French social charges — an S1 is the simplest proof if you hold one, but Form A1 or an equivalent certificate work too, so this isn't limited to S1 holders
• HMRC's non-resident CGT report is due within 60 days of completion — considerably tighter than the equivalent French deadline for a French property

Someone sells a UK buy-to-let while living in France, pays the HMRC bill, and assumes that's the end of it. It isn't. The same gain has to be declared in France too — and because two different tax systems are involved, with different rates, different allowances, and a treaty credit that only covers part of what's due, this is genuinely more complicated than selling a French property.

This article is specifically about a UK property sale by someone who is a French tax resident. If you're selling a French property instead, the calculation is different and considerably simpler — see Capital Gains on a French Property Sale: How It's Calculated and Declared. If the UK property was your primary residence before you moved to France, get that checked separately, since a former home carries its own rules that this article doesn't cover.

Step One: The UK Side Comes First

Because the property is in the UK, the UK taxes it first, under its own rules — regardless of where you live.

Non-resident Capital Gains Tax (NRCGT) applies to a UK property owned by someone who lives outside the UK, at 18% or 24% on residential property, depending on your UK income tax band for the year of sale. This is a UK calculation, using UK rules — the French 19%/17.2% rates and the 22/30-year allowance schedule that apply to a French property sale don't feature anywhere in this step.

Important note:

• Rebasing to April 2015. If you owned the property before 6 April 2015, you can generally use the property's value on that date as your starting cost, rather than what you originally paid decades earlier — meaning only the gain since 2015 is taxable in the UK, not the entire lifetime gain.
• The 60-day reporting deadline. HMRC requires a non-resident Capital Gains Tax return and payment within 60 days of completion — considerably tighter than the equivalent French declaration window for a French property sale, and it's easy to miss if you're mentally applying French deadlines to a UK sale.
• The annual exempt amount. The first £3,000 of gains in a tax year is entirely free of UK CGT, for an individual. It doesn't carry forward — unused allowance in one tax year is simply lost, not banked for next year.

What You Can Deduct Before the UK Rate Applies

The UK gain isn't simply "sale price minus purchase price" either — HMRC lets you deduct genuine costs on both sides before the 18%/24% rate touches anything.

Added to your acquisition cost:

• The original purchase price
• Stamp duty paid when you bought the property
• Legal fees and survey or valuation fees from the purchase

Added as improvement costs (not routine maintenance):

• Genuine capital improvements — an extension, a new kitchen fitted where none existed, structural work — count
• Ordinary repairs, redecoration, and maintenance do not count, even if the work was extensive

Deducted from your sale price:

• Estate agent fees
• Legal fees on the sale
• Other direct, incidental costs of selling

Unlike the French flat-rate options on the companion article for a French property, there's no equivalent flat-rate shortcut here — HMRC requires actual costs, generally with some form of record or receipt, for all of these.

Step Two: Declaring the Same Gain in France

Once the UK side is settled, the same gain still needs declaring in France, because French tax residents are taxed on worldwide income and gains — a UK property sale doesn't sit outside that just because the UK taxed it first.

The gain is declared via Form 2047 (the foreign income annex) alongside your main Form 2042 return, feeding into Box 3VZ. For the full picture of how foreign income and gains fit into your French return generally, see Form 2047 Explained: How UK Expats Declare Foreign Income in France.

France then calculates its own tax on the gain — 19% income tax plus social charges — but you're not simply taxed twice on the full amount. This is where the treaty comes in.

The Treaty Credit: What It Covers, and What It Doesn't

The UK-France double tax treaty (specifically Article 24) provides a credit against French income tax equal to the UK tax you already paid on the same gain, so you're not paying full income tax twice on one sale.

This is where it gets genuinely important, and where the confusion usually starts: the credit reliably covers French income tax. Whether it extends to French social charges is a narrower, less settled question — sources disagree on the precise scope, and this is worth confirming with an accountant familiar with both systems rather than assuming either way. What is clear is that a meaningful portion of French social charges will be due regardless of what you paid HMRC, because of how the two social-charges components below actually work.

Reconciling a UK CGT bill against a French treaty credit, on top of working out which portion of French social charges still applies, is exactly the kind of cross-border calculation worth getting checked by an accountant before you file — a small error here either leaves money on the table or creates a genuine underpayment.

The Two Parts of French Social Charges — and Why They're Treated Differently

French social charges on this type of gain are actually two separate components, and they behave differently depending on your circumstances:

CSG and CRDS (the bulk of the 17.2% headline rate) — since a 2021 rule change following Brexit, a seller who can prove they're affiliated with UK social security rather than French social security is generally exempt from this portion, the same exemption that already applied to EEA-affiliated sellers.

An S1 certificate is the proof most retired UK expats will already hold, and it works directly for this purpose. But S1 isn't the only accepted document, and it isn't a requirement in itself — it's one of several ways to prove the same underlying fact. Form A1 (proof of which country's social security system currently covers you) or an equivalent affiliation certificate from your UK institution work just as well. In practice, this means the exemption isn't limited to pensioners with an S1 — someone of working age still paying UK National Insurance, who has never held an S1 at all, can also qualify, as long as they can produce one of these documents.

The 7.5% solidarity levy (prélèvement de solidarité) — this portion stays due regardless of which social security system you're affiliated with. It funds general government spending rather than the French social security system, so the exemption above doesn't touch it.

If you do hold an S1, that's the simplest route to claiming the CSG/CRDS exemption — for the fuller picture of how an S1 changes what you owe more broadly, see How to Stop Paying Social Charges on Your UK Pension in France. If you don't hold one but are still UK-social-security-affiliated, ask your notaire or accountant what alternative proof (Form A1 or an equivalent certificate) they'll accept instead.

What to Do Now

1. Deal with the UK side first: confirm your NRCGT rate, check whether April 2015 rebasing reduces your taxable gain, and file within the 60-day HMRC deadline.
2. Gather records of your acquisition costs, genuine improvement work, and selling costs — these reduce the UK gain, but HMRC wants actual figures, not a flat-rate estimate.
3. Check whether your £3,000 annual exempt amount is still available for the tax year of sale — it's lost if unused, not carried forward.
4. Declare the same gain in France via Form 2047/Form 2042, feeding into Box 3VZ — don't assume paying HMRC is the end of your obligation.
5. Get the treaty credit calculation checked by an accountant rather than assuming it wipes out your full French bill — it reliably covers income tax, but the social charges position is less clear-cut.
6. Confirm which document proves your UK social security affiliation — an S1 if you hold one, otherwise Form A1 or an equivalent certificate — and raise it with your notaire; it's likely to remove the CSG/CRDS portion of what you'd otherwise owe, leaving the 7.5% solidarity levy as the main remaining French charge.

For more on cross-border declaration questions like this one, see the Strategies & Pitfalls category.

Common Mistakes

1. Applying the French 22/30-year holding-period allowance to a UK property. It doesn't apply — a UK property's gain is calculated entirely under HMRC's own rules first, including UK-specific rebasing rules, not the French schedule.
2. Assuming a French-style flat-rate deduction is available on the UK side. It isn't — HMRC wants actual acquisition, improvement, and selling costs, generally with records or receipts, not a percentage shortcut like the 7.5%/15% flat rates available on a French property sale.
3. Assuming the treaty credit wipes out the entire French tax bill. It reliably offsets French income tax against UK tax paid — the social charges position is narrower and less settled, and shouldn't be assumed away without checking.
4. Missing the 60-day HMRC deadline because you're thinking in French timeframes. The UK reporting window is considerably tighter than what applies to a French property sale, and it runs from completion, not from the end of the tax year.
5. Assuming you need an S1 specifically to claim the CSG/CRDS exemption. An S1 is the simplest proof if you have one, but it isn't the only route — Form A1 or an equivalent UK affiliation certificate work too. Someone still paying UK National Insurance who has never held an S1 can still qualify.
6. Forgetting the property sale still needs declaring in France even though HMRC already taxed it. French tax residency means worldwide income and gains are in scope — paying the UK first doesn't remove the French declaration obligation.

Frequently Asked Questions

What costs can I deduct from a UK property gain?

Genuine acquisition costs (purchase price, stamp duty, legal and survey fees), capital improvement costs (an extension or new kitchen, but not routine repairs or redecoration), and selling costs (estate agent fees, legal fees on the sale). Unlike a French property sale, there's no flat-rate shortcut — HMRC wants actual costs, generally supported by records or receipts.

Do I use the French 22-year and 30-year allowance rules for a UK property sale?

No. Those allowances apply only to a French property sale under French rules. A UK property's taxable gain is worked out entirely under HMRC's non-resident Capital Gains Tax rules, including the option to rebase the property's value to April 2015 — a different calculation altogether.

If I've already paid UK Capital Gains Tax, do I still owe anything in France?

Likely some social charges, even after the treaty credit is applied. The credit reliably covers French income tax against UK tax already paid, but French social charges are calculated separately, and the portion covered by the credit is a narrower, less settled question worth confirming with an accountant rather than assuming resolved.

Do I need an S1 to reduce what I owe in France on a UK property sale?

No, though it's the simplest way if you already have one. What actually matters is proving you're affiliated with UK rather than French social security — an S1 does that, but so does Form A1 or an equivalent UK affiliation certificate. This exempts the CSG/CRDS portion of French social charges on the gain. The 7.5% solidarity levy typically remains due regardless.

What's the deadline for reporting a UK property sale to HMRC?

60 days from the date of completion, considerably tighter than the equivalent timeframe for declaring a French property sale. This applies to non-UK residents specifically, under the Non-Resident Capital Gains Tax reporting rules.

Do I still need to declare a UK property sale in France if I already paid UK tax on it?

Yes. French tax residents are taxed on worldwide income and gains, so a UK property sale needs declaring on your French return via Form 2047 and Box 3VZ, regardless of what was already paid to HMRC. The treaty credit is what prevents this from becoming full double taxation, not an exemption from declaring it at all.

Sources: Non-residents and capital gains tax — Low Incomes Tax Reform Group (UK non-resident CGT rates, the 60-day reporting deadline, and April 2015 rebasing) · Plus-value immobilière : les résidents britanniques peuvent également bénéficier de l'exonération de CSG et de CRDS — Haussmann Patrimoine (confirms the post-Brexit CSG/CRDS exemption for UK-affiliated sellers, and that the 7.5% solidarity levy remains due) · Fiscalité en matière immobilière — La France au Royaume-Uni (French Embassy, UK) (confirms the Article 24 treaty credit mechanism for French residents selling UK property) · Reducing the annual exempt amount for Capital Gains Tax — GOV.UK policy paper (confirms the £3,000 annual exempt amount, permanently fixed from 2024/25 onward, and that it does not carry forward) · Expatrié : comment bénéficier de l'exonération CSG-CRDS ? — Banque Transatlantique (confirms the accepted proof documents for the CSG/CRDS exemption — Form S1, Form A1, or an equivalent affiliation certificate from the foreign institution — and that the exemption is based on social security affiliation, not specifically on holding an S1)