I take it you're in France and you have your sécu number? If that's the case, then you need to specify what you're refering to by "taxes."
Depending on the sort of job you have and how you're paid, you will most likely have about 20 - 25% of your pay taken to pay for cotisations (which are social charges - health care, retirement, etc). - and not technically "taxes" though most folks think of the that way.
At the end of the year - actually in May of the year following the tax year - you then file your tax declaration. How much you will have to pay when the assessment is received (in August or September) depends on many factors, including your total worldwide income and your family status (married or single, how many children or other dependents).