When to quit H1b and transfer to a new h1b?

Question

I work for a company and got a new job now. My attorney filed for LCA and it is approved for h1b.
How early can I start working
1. if h1b filed and delivered to USCIS
2. what about after reciept from USCIS of h1b or after approval

Answer 1

as soon as the H-1B is filed you can do it.

Also, I would suggest wait for USCIS to issue the case receipt, as properly filed, before actually "jumping ship" and starting to work for the new employer.