I am a Tunisian national on J1 Visa in the US. However, I have never paid taxes in Tunisia. I did my PhD and was working in France for 5 years paying taxes there. I got my visa in France. Is my tax residency France or is it Tunisia? Because if I claim it to be Tunisia, there is no two years tax treaty. If it's France, what documents I need to claim the tax refund?
Tax treaties are based on tax residency (country where you last paid income tax before arriving to the U.S.) not nationality or country of citizenship. For that reason you do qualify for exemptions provided by tax treaty between France and the United States.
As J-1 visa holder you are exempt from filling/paying FICA (Social Security and Medicare) taxes. Above mentioned tax treaty will also exempt you from paying federal taxes as well. Many of the individual states require state income taxes to be withheld on this income. California is one of them.
US/France tax treaty & federal tax exemption:
• Teaching or Research: 2-year exemption & no income limitation
• Studying or Training: 5-year exemption & $5,000/year income limitation (first $5,000 is reported on form 1042-S and the rest on form W-2)