Can The IRS Revoke My Passport?

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.

What are the best ways of spending money apart from spending just on shopping and entertainment? When can spent money be never regretted? Add your feedback please.

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

If I'm participating in my employer's 401K plan, may I also set up a SEP-IRA for my self-employment income?

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

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?