Your first French tax return: the British arrival's survival guide

Of all the French admin a British arrival has to face, the annual tax return is the one that generates the most quiet dread — and the most misinformation over a glass of something at the local marché. "You don't need to bother in your first year." "My pension's taxed in England, so France isn't interested." "ISAs are tax-free, obviously." Every one of those is wrong, and each can cost you. So let's take it slowly, in the order it actually happens.

The single most important thing to understand up front is that filing and paying are two different acts. France asks residents to declare their entire worldwide income every spring. That's a disclosure exercise, and it's compulsory. What you then owe is a separate question, settled by the France–UK double-tax treaty, and for a great many British retirees the answer is "less than you feared, and sometimes nothing at all." Declaring is not the same as being taxed twice. Hold that thought — it defuses most of the panic.

Do you even have to file? (Almost certainly, yes)

France decides you're tax-resident — domicilié fiscalement en France — if you meet any one of four tests: your home (foyer) is here, you spend most of your time here (the "183 days" rule), your main work is here, or the centre of your economic interests is here. Crucially, you only need to trip one wire. A retired couple who move their home to the Tarn are resident from the day they arrive under the foyer test — they don't get to wait until they've clocked up 183 days.

In your year of arrival, France only taxes you on income from the date you became resident — not the whole year. Income you earned in the UK before you packed the removal van generally stays outside the French net. After that first part-year, you're declaring worldwide income for the full calendar year, every year.

Why your first return is on paper

France's online system is genuinely good — but you can't get into it in year one. Logging in needs three identifiers: a numéro fiscal, a numéro d'accès en ligne, and last year's revenu fiscal de référence. A brand-new arrival has none of them, because you've never been assessed here. So the first return is done the old-fashioned way, on the paper formulaire 2042, posted to the Service des Impôts des Particuliers (SIP) for your commune.

That first paper return is what breaks the chicken-and-egg. Once the SIP processes it, they issue your numéro fiscal, and the resulting avis d'impôt hands you the two other numbers you need. From year two onward you file online — and once you have internet access, online is mandatory. Some tax offices will, if you ask nicely and early, issue a numéro fiscal in advance so you can go straight online even in year one; it varies office to office, so treat paper as the reliable default and a pleasant surprise as the exception.

The 2026 calendar

The 2026 season covers the income you received in 2025. The online service opened on 9 April 2026, and the deadlines are staggered so the whole country doesn't file on the same night:

Miss the date and you'll face a late-filing surcharge, so if your first year is paper, post it well before 19 May and keep proof of postage — the postmark counts.

UK pensions: how the treaty carves them up

This is the heart of it for most British arrivals, and the part worth reading twice. The France–UK double-tax treaty (signed 2008) sorts your UK pension income into three boxes, and which box a pension falls into decides which country taxes it.

So, in plain terms: your UK State Pension and most private or occupational pensions become taxable in France, at French rates. To stop the UK taxing them as well, you file HMRC's France-Individual form, which switches off UK PAYE and lets France tax them instead. Your UK government or civil-service pension — NHS, teacher, armed forces, police, local authority, civil service — stays taxable in Britain. But you still write it on your French return, because France uses it to calculate the taux effectif: the effective rate it then applies to the rest of your income. The government pension itself isn't taxed twice; it just nudges the rate on everything else upward.

Mechanically, all of this foreign income lands first on form 2047 (foreign income), then flows onto the main 2042. The government-pension credit is reported at box 8TK. You don't need to memorise the box numbers — but you do need to know the income exists and belongs on the form.

Declaring your UK accounts: the €1,500 trap

Here's the one that catches the most careful people. As a French resident you must declare every foreign account you hold, use, opened or closed during the year — on form 3916 (and 3916-bis for app-based and crypto accounts). Not just the account your pension lands in. The dormant UK current account you keep "just in case." The old building-society savings book. The Revolut or Wise app you use for transfers. The ISA. All of them.

The bit that saves you money: social charges and the S1

Income tax is only half the picture in France; there are also social charges (prélèvements sociaux — CSG, CRDS and friends). And this is where British retirees have a quietly valuable advantage that many don't claim.

Under the European coordination rules that the Brexit Withdrawal Agreement preserves, if your healthcare is the responsibility of another state — that is, if you hold a UK-issued S1 form because your NHS-funded cover is charged to Britain — then you're exempt from CSG and CRDS on your pension. In practice that means an S1 holder pays no social charges at all on UK pension income. And on investment or rental income, the S1 knocks the social-charge rate down from the full 17.2% to just the 7.5% solidarity levy. That's not a rounding error — on a decent investment portfolio it's a meaningful sum every year. Make sure your return reflects your S1 status.

Why year one feels oddly quiet — then doesn't

France collects tax at source (prélèvement à la source) — but there's no French payer to withhold anything from a UK pension. So for a new arrival, nothing is deducted during the first year. You typically pay no French income tax in year one. Then, once your first return is processed and your avis is issued (usually the following late summer), the tax office sets up monthly or quarterly instalments — acomptes — drawn straight from your French bank account. The first of these can feel steep, because it may bundle several months of catch-up at once. It's not a penalty; it's simply the system starting late and squaring up. Budget for it and it won't sting.

The first-timer mistakes, gathered in one place

To save you the pain of learning these the hard way: don't skip the return because you're new or because your pension is UK-taxed — everyone resident files. Don't try to file online in year one and then miss the deadline when the login won't work — go paper. Don't forget form 3916 and a stray account. Don't leave your government pension off the return just because Britain taxes it. Do file HMRC's France-Individual form so you're not paying UK tax on income France should be taxing. Do claim your S1 exemption from social charges. Do convert sterling to euros using the year's official rate. And do expect the payment lag, so the autumn acompte doesn't ambush you.

None of this is a substitute for a good accountant in your first year or two — a cross-border specialist will pay for themselves by getting the treaty positions and the social-charge exemptions right from the start. But walking in understanding the shape of it means you'll know whether the advice you're getting is sound, and you won't sign up to be taxed twice on anything.

This guide offers practical, general information, not tax, legal, or financial advice. Pimpernel are not accountants, notaires, or tax advisers. French tax residency, the France–UK treaty, social charges, filing dates, and the figures quoted change, and how they apply depends entirely on your own circumstances — your residence, your income mix, your S1 status, and your family situation. Deadlines and thresholds shift each year, so always confirm the current figures on impots.gouv.fr and take advice from a qualified cross-border accountant before acting.