I am currently on OPT that will expire June 2007. In the meantime, my H1B has been approved for Oct 2006 onwards. On OPT I don't have to pay extra taxes for Social Security and Medicare but I guess as H1B I will have to. Now let's assume I get my h1B stamped on Nov 25.

1. Am I right that up to Sept 30, SS/Medicare taxes will not be deducted?
2. Am I right that Nov 25 onwards these taxes will be deducted?
3. What happens between Oct 01 and Nov 24? Are SS/medicare taxes deducted?

I am just trying to see if deferring the H1B stamping would give me a tax break on the SS/medicare front. Also if I do defer the stamping, what are the disadvantages (of course, I can't travel out of the country and come back without a visa)?

Thanks much for any pointers.

Since you H-1B visa becomes effective in Oct 2006, that is when you become liable for Social Security and Medicare taxes. Your obligation begins and ends when you tell your employer when the H-1B visa becomes effective. After that, it rests with your employer to begin withholding these taxes.