Can I transfer from A to C, while working on B with pending approval?

Hi, I switched from A to B a week ago on H-1B receipt notice. My H-1B with A is valid until March 2019 and i-94 has the same date. Company C had filed my H-1B while I was with A. Now company C wants me to join them on H-1B receipt. Company C is reputed and like my dream job. I really want to work with them. If I have paySlips from B that means I was never out of status. Am I obliged to tell C that I worked with B ?

Well, it depends on timing of the filings from B and C. Sometimes, there could be bridge situation where you are joining C using B as bridge, then it can get tricky. It is not just about moving around or getting payslips. Sometimes, there could be implications, if a denial happens with B as it maybe bridge. You should talk to an attorney and discuss your scenarios and take an informed decision.