Question: My H-1B is with Employer A with I-140 approved for more than 3 years, have new job offer with employer B who is ready to file for my H-1B transfer. If H-1B with employer B gets approved, do I have to start working for employer B or can i still stay with employer A?

Answer: It is advisable to move according to the transfer to avoid confusion with the USCIS and site visits. However, the transfer works as a job offer, which you have an option to take or reject. Once you move to the second employer, you will have to transfer back to the first employer as the underlying case is being assumed as being overtaken.