I got a post-doc offer in France with a net salary 2000 euro. Which means social security contributions already deducted, right? What will be my salary after paying income tax? I am married and have one child, but they are not residing in France. They live in my home country.
You are right that net means what you get on your account, health coverage, social security and retirement contributions are deducted.
You still have to pay income taxes on that net income.
The exact amount to pay as income tax will greatly vary depending on the fact that your family is actually included (personnes à charges, revenu du foyer) or not, I am not able to confirm you what will be considered in your case.
There's a simulator here : https://www3.impots.gouv.fr/simulateur/calcul_impot/2018/simplifie/index.htm
A simulation of 24000 € of net income for a married couple plus one minor child leads to 0 € of income tax.
A simulation of 24000 € of net income for a single person leads to 1651 € of income tax.
Notice that from 2019, income tax will be deducted monthly from you payslip, but that might not be the case for you if it's your first year working in France.
You will have to ask your (potential) employer. Personally I would expect that to be 2000 euro net of income tax, but you might also have to pay:
- social security costs (this is the least likely)
- health insurance
- pension contributions
I don't know the system in France, but if you leave France after a short while, you may be able to get your pension contributions back.