回複：h1->h1

I just did H1b transfer, the minute you get reciept for new H1b, you will be able to work. My friend's lawyer told her she could start working once she got the USPS delivery confirmation card (not necessarily the offical INS reciept), she could start work.
You can have some gap between your two jobs as long as your old H1b does not expire. My lawyer told me I can have upto 3 month break in between, which I doubt. But I did take a week break between my two jobs.
Hope this helps. But you'd better consult with your lawyer.