I worked for several years for a employer that did not pay social security neither medicare. Now at my new job I have to pay it. I have 3 questions

Does H1b holders have to pay Social and medicare?

Do I have to pay social security and madicare for the time I work for my last employer? How can I do that?

I apreaciated your help.

Yes, holders of the H-1B visa MUST PAY Social Security and Medicare taxes.

No, you do NOT have to pay the back taxes. The IRS holds the EMPLOYER responsible to collect these taxes from the employee and pay them in a timely manner. The last date such taxes could be reconciled for 2006 is 31 January 2007.

The only way to pay these taxes is through the employer. If the employer failed to withhold them from your salary and pay them when due to the IRS, he will be liable to a huge fine if he brings the matter to the IRS' attention. I doubt very much that the employer will want to do that.

What about non resident h1b holders who have not entered the us on h1b? The current income is from non-employee compensation and not based on h1b.

Do such individuals need to pay social/medicare?

OK... I will try to answer my question=> FICA taxes are supposed to be withheld from the pay by my employer. I don't have to worry about it and just need to fill in the 1040NR asap... right?

update!

=> IF you are not in U.S soil and are providing services to the U.S, your income is not taxable ( irrelevant of the visa type you are holding)

In other words, if you have h1b and have not entered us on that visa, but you are still providing services as an independent contractor, then you donot need to pay any taxes.

Your update is correct.