The fine for an undeclared foreign account is €1,500 per account, per non-time-barred year. It rises to €10,000 if the account sits in a state with no administrative assistance agreement with France. This is not a tax on what the account earned: it is a flat fine, due even if the account is empty and never produced anything.
That asymmetry is what makes this topic serious. Here are the most common mistakes, ordered by what they cost.
Assuming no gain means nothing to declare
The 3916 declares the account's existence, not its results. 1,500 EUR per account, even at a zero balance.
Forgetting neobanks
Revolut, N26, Wise: a foreign account is a foreign account, even if used for one holiday.
Confusing 3916 and 3916-bis
The second covers digital-asset accounts. A self-custodied wallet is not an account; a platform account is.
Declaring in foreign currency
Everything is declared in euros, converted at the transaction's rate, not at the 31 December rate.
Forgetting to deduct fees
Brokerage and FX fees belong in the acquisition price. Leaving them out inflates the declared gain.
Not declaring losses
An undeclared loss is a lost loss: it carries forward ten years, but only if it was reported.
Believing the platform files for you
A broker tax report is not a tax return. You remain solely responsible for what you file.
None of them is a forgotten gain: they are mistakes about scope, about the form, or about currency. The 3916 fine is due even when the account is empty and nothing was earned.
1. Assuming "no gain" means "nothing to declare"
By far the most widespread mistake. The obligation to declare an account opened, held, used or closed abroad (form 3916) is entirely independent of what the account produced.
A Revolut, N26, Wise or Trade Republic account opened out of curiosity, holding €12 and never used, must be declared. An account closed during the year must be declared for that year. An account that lost money must be declared.
The good news: that declaration costs nothing. It is an administrative box, not a tax. Forgetting it, on the other hand, costs €1,500.
2. Forgetting that neobanks count
Many people diligently declare their brokerage account abroad and forget the payment account they opened in three minutes on their phone.
The type of account is not the criterion: location is. An account with an institution headquartered in Lithuania, Ireland or Germany is a foreign account, even if the app is in French, even if your salary lands there, even if it is only for holidays.
The habit to build: list every financial app installed on your phone. That is usually where the omissions hide.
3. Confusing 3916 and 3916-bis (and getting wallets wrong)
Since 2020, digital-asset accounts have their own reporting regime. The distinction that matters:
- An account with a third-party provider established abroad (Binance, Kraken, Coinbase…) must be declared.
- A wallet whose private keys only you hold (Ledger, Trezor, MetaMask…) is in principle not an account opened with a third party, and therefore falls outside this obligation.
The classic error runs both ways: declaring a Ledger out of excess caution, or not declaring a Binance account because "crypto isn't a bank account". The second one is the €1,500 mistake.
4. Declaring amounts in foreign currency
French forms expect euros. A gain realised in dollars must be converted, and not at the rate on the day you fill in your return: at the rate applicable on the date of each transaction.
In practice, for a sale in dollars, the purchase converts at the purchase-day rate and the sale at the sale-day rate. That double conversion is why a trade can be profitable in dollars and loss-making in euros, or the reverse. On an active portfolio, redoing this by hand is the surest way to get it wrong.
5. Forgetting to deduct fees
Taxable gain is computed on the sale price net of fees, minus the acquisition price increased by purchase costs. Brokerage commissions, FX fees, transfer fees: anything directly tied to the transaction reduces the taxable base.
Many people declare the raw difference between two prices. At the 31.4% flat tax, overlooking €400 of fees in a year means roughly €125 paid for nothing.
6. Not declaring your losses
The most counter-intuitive mistake: you declare when you lose, too.
For securities, a capital loss offsets same-nature gains for the year and can then be carried forward for ten years. For digital assets, gains and losses of the year offset each other.
Not declaring a bad year means giving up a credit that would have cut the tax on later years. It is a gift to the tax authority, entirely voluntary.
7. Believing "the platform declares for me"
A foreign broker has no obligation to issue a French-style tax statement. Some provide a "tax report", which helps, but that document remains the broker's calculation, not a declaration.
Two cautions follow. First, those reports do not always follow French rules, particularly the cost-basis method. Second, automatic exchange of information between tax administrations is very real: the authorities may know an account exists without that relieving you of declaring it. Being asked to explain why a known account is missing from your return is a very concrete scenario.
What to remember
French logic separates two things people routinely merge:
| Obligation | Triggered by | Cost if missed |
|---|---|---|
| Declaring the account (3916 / 3916-bis) | Its mere existence | €1,500 per account per year |
| Declaring the gains (2074, 2086, 2047) | A disposal, an income | Back tax + interest + penalties |
The first is free and purely administrative. There is therefore no rational reason to skip it: you gain nothing by not declaring an account, you only risk a flat fine.
And if you discover an omission on past years, voluntary disclosure is generally far more favourable than being audited. The topic deserves a professional, but inaction is the worst option.
Where IgniFI comes in
What it does not do, and never will: file for you. The figures are prepared, you check them against the official guidance, and the return stays yours. For complex situations, an accountant or tax lawyer remains the right person to ask.