you don't have to declare your crypto if you convert them to a fiat currency

In France, capital gains on cryptocurrency sales must be declared annually when filing your income tax return. Filing deadlines vary depending on your place of residence.

For 2024, the deadlines were as follows:

• Departments 01 to 19: until May 23, 2024.
• Departments 20 to 54: until May 30, 2024.
• Departments 55 to 976: until June 6, 2024.
• Paper declaration: until May 20, 2024.

These dates may change each year. It is therefore recommended to regularly consult the official website of the French tax administration to obtain the most recent information. 

To declare your digital assets, you will need to complete the following forms:
• Form 2042 C: to declare capital gains or losses on digital assets.
• Form 2086: to detail digital asset transfers.
• Form 3916-bis: to report digital asset accounts held abroad.

Make sure you comply with these reporting requirements to avoid potential tax penalties.