France · Foreign law before the notaire · Information, not legal advice — as at 25 August 2026
Why the French notaire asks for a certificat de coutume — and who can give one
A certificat de coutume — in English terms, a certificate of foreign law (the same job an affidavit of law does in common-law courts) — is a formal written statement of foreign law, given by a lawyer qualified in that law, which lets a French notaire apply it to the succession — proving, for example, that an English will is valid, what its words mean, who takes under English intestacy, or that an election of English law under Brussels IV works. French practice has no fixed statutory form: what matters is the author’s qualification and the precision of the answers. For a British estate it typically must arrive in French (or with a sworn translation) and answer the notaire’s exact questions — which is why generic templates get rejected and files stall. We produce these certificates in-house, in French, as the regulated English- and Irish-qualified lawyer also registered at a French bar — usually the fastest single fix on a stalled Franco-British succession.
Every Franco-British estate reaches the same moment: the notaire — who by law leads the French settlement — must apply English law to something. Perhaps the will is English and its validity and meaning must be established. Perhaps there is no will, and English intestacy decides who takes. Perhaps the will elects the law of England and Wales under Brussels IV and the notaire must know what that law actually says before drawing the acte de notoriété. A French notaire is not required to know English law — and will not guess at it. Foreign law must be proven to the notaire, as a fact. The instrument French practice uses is the certificat de coutume — literally a “certificate of custom”, in substance a certificate of foreign law, the cousin of the affidavit of law an English or Irish court would expect.
What the certificate actually is
A formal written statement of the foreign law, given by someone qualified in it — classically a lawyer admitted in the relevant jurisdiction. There is no statutory template: its authority comes from the author’s qualification and the quality of its content. A good one reads like a short legal opinion: it identifies the question the notaire must decide, states the governing rules with their sources, applies them to the estate’s facts — this will is formally valid; these are the persons entitled, in these shares; this election is effective — and signs it with the author’s credentials. A poor one — a generic paragraph unmoored from the file — is precisely what notaires reject, and a rejected certificate can stall a succession for months.
What the notaire typically needs it to cover, for a British estate
The recurring questions: the formal validity of the English or Irish will; its meaning — English drafting (executors, trusts for sale, residuary gifts) does not map neatly onto French concepts and needs translating in substance, not just language; who takes on intestacy where there is no will; the effect of a Brussels IV election; and, often, how English law and the French machinery interact — because whichever law governs who inherits, the French property still transfers through the French process, with the notaire’s acte and the déclaration de succession running in full. Since Brexit, no European Certificate of Succession can paper over any of this for a UK estate — the UK never joined that system — so the certificat de coutume carries more weight on Franco-British files, not less. (And where the family asks about the 2021 “clawback” over French assets — article 913, and where it stands in 2026.)
Who can give one — and why in-house matters
The notaire needs an author whose qualification they can rely on: a lawyer admitted in the foreign jurisdiction whose law is being certified. In the usual chain, the French notaire writes to an English firm, waits, receives an English-language opinion, and then has it sworn-translated — three parties, two languages, months. We compress the chain to one step: as an English- and Irish-qualified solicitor who is also the registered European lawyer at a French bar, we produce the certificate in-house, in French, addressed to the notaire’s exact questions — one author, no translation round-trip, no relay of emails across the Channel. And France is not alone — the same proof is demanded, under other names, in all four of our countries: the Spanish notario asks for a certificado de ley (or a sworn legal opinion on the foreign law), the Italian notaio equally requires English law formally attested before acting on it, and the Portuguese notary needs the certificate of English law before an English will can move a Portuguese asset. It is the same document, produced for each authority in its own language — our certificates of foreign law, each at a published fixed fee (free where we administer the estate).
If a notaire has asked your family — or your firm — for a certificat de coutume, that request is usually the only thing between the file and its completion. Send us the notaire’s letter and the will, and we will tell you exactly what the certificate must say, what it costs, and how quickly it can be on the notaire’s desk. And if you are the English solicitor on the estate, the professional walkthrough is the English solicitor’s guide to the French estate.