What is the difference between the gross and net interest rate?

Hello,

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?
Thanks

I am a Nonresident Alien and I live in Ensenada Baja California Mexico. I’m about to buy many electronics. Total value would be around $12,000 for my personal use. I am building my own house and I want to buy from SEARS in Chula Vista, California, but I don’t want to pay double tax (in the US and Mexico) since I am going to import the merchandise to Mexico. Is there any way to avoid the payment of taxes in Chula Vista?

I am doing freelancing for two different companies and I have several questions. I deliver for them digital files, such as research, PowerPoints or excel files. Do I need to add sales tax to the invoices? When and how do I file taxes? I have never worked before in California and just started working in October last year.

Can I claim child tax credit for my son born on December 31?

What is a Future Delphi credit scoring and how does it work?

How many people actually go in for a Health Insurance? It is observed that most people think it is a waste of money so avoid it. What do you think?

When can I file my 2017 tax returns?