H1B transfer approved while extension is pending

Hello Members,I am currently working with an Employer A on H1-B Visa and my H1-B expires in Sept 16 2015 (eligible for Renewal). My Company A is about to start the H1-B Extension for me in few days or they had had already filed my h1B extension (not sure).Meanwhile I got an offer from company B and they applied my H1B transfer in PP and today I got the approval.

I would like to know what will happen if I resigned from my current Employer (A).

Do I need to wait for my extension to come through (which will take more than 2 months) or I can join my new employer while extension is pending?

I might comeback to current employer (A) if things don’t well in Company B.So usually what employer does when extension is pending and someone resigned?

I mean are they legally obliged to withdraw the extension application or it is up to them to go for extension or withdraw it?

I would appreciate any help you could provide.

Thanks

Sweta Verma

You can start working with B immediately.