Self-correcting is always better than waiting for an audit
If you realise you've made an error in your return — forgotten income, excessive deduction, incorrect family situation — correct it yourself as soon as possible. Self-correction drastically reduces penalties. An error discovered by the tax authorities during an audit costs far more than a voluntary correction: 10% for unintentional errors reported voluntarily, versus 40% for deliberate non-compliance discovered by the tax office.
Online correction: simple and quick if you act early
Until 15 December of the tax year, you can correct your return directly online at impots.gouv.fr. Log into your personal account, open your return, click "Corriger ma déclaration" and change what needs correcting. The correction is automatically processed and a new tax notice is sent to you if the amount changes.
After 15 December: a contentious claim
After that date, you need to send a contentious claim to your Service des Impôts des Particuliers by recorded letter. You have this right until 31 December of the second year following the tax assessment. In your claim, precisely explain the error, state the correct amount, and attach relevant supporting documents.
The most common errors to watch out for
Among the most common omissions: income from side jobs or secondary activities, rental income if you're subletting, dividends or investment interest, incorrectly stated maintenance payments received or paid, and changes in family status (marriage, divorce, birth) that affect the number of tax shares.
You declared too much income by mistake?
If you over-declared, you've overpaid tax. The same correction procedure applies — and in this case you can get a refund of the overpayment. The tax authority has 6 months to process your correction request and issue the refund.