回复：H1转了以后的工作问题

You mean your first H1b start date 是本月20号? Basically by law when your status changed into H1b,you need pay social and medicare tax from the date you got H1b, as we know,as a student in OPT period, you need not pay SS and Medicare tax. Then you need pay SS and Medicare tax beginning on 12/20/04. But who cares about that 10 days tax difference!!!
However, to be safe, now it's better to ask your employer to pay SS and Medicare tax and withhold that tax for your coming payment period.