回复：回复：无人回答还得问:H1-B变更雇主，谢谢答复

Why is his old H1 invalid once he submitted his old ID? A person can carry several H1b but work full-time for only one employer. I don't know if it's required for the HR to withdraw H1b once that employee resigns from the position. I've heard people go back to the old position after quitting job with the new employer (he already has a new H1b with the new employer) without applying for a new H1b again. The reason is because he has an old H1b with the old employer and it's still valid when he decides to go back to the old employer. Correct me if I'm wrong.