Hi

I am on H1 since Oct 2007 and was on F1 before that. My company never deducted my social security/medicare and even I was unaware of any such tax. Today I got an email from my company saying I need to pay all taxes starting oct 2007 to the company as company has already paid them. Question is : legally can the company force me to pay back dated taxes. One of my colleague who started with me left the company recently, so how does the company recover taxes from him. The point is if I leave the company now I won't have to pay those taxes?

Thanks

My son received a W2 from his work with taxes deducted, but also 1099 without deductions. Does he have to pay Social Security tax on the 1099 and where do I enter the SS tax?

Your H1-B income is subject to SS tax and Medicare care. Evidently, your employer made a mistake by not withholding FICA taxes from your income.
Now your employer wants you to pay it so you must pay it. They can legally claim it from you.
Read about H1-B tax filing: Your U.S. Tax Return: The U.S. Visas