h1 to h4 to h1

[iamdeb]

My wife had H1b visa with validity from Oct 2011 to Sep 2014. She worked on that H1b visa from Oct 2011 till Jan 2013. Then her project ended and she transferred to H4 visa on Jan 2013.
Now she has got a job offer and an employer is willing to do the new H1b filing. How soon can she start working? Can she join work as soon as her H1b receipt is generated? Or does she have to wait for the H1b to be approved before she can work?

[Spectator]

My wife had H1b visa with validity from Oct 2011 to Sep 2014. She worked on that H1b visa from Oct 2011 till Jan 2013. Then her project ended and she transferred to H4 visa on Jan 2013.
Now she has got a job offer and an employer is willing to do the new H1b filing. How soon can she start working? Can she join work as soon as her H1b receipt is generated? Or does she have to wait for the H1b to be approved before she can work?

iamdeb,

My understanding is that, since she is not currently in H1B status, she cannot start working until the H1B petition is approved.

Working based on the receipt is only possible when the person is already in H1B status, for example when changing employers.