How soon can I transfer my H1b after approval?


I Completed my Masters here in the USA and I was in my last year of extended OPT. My employer filed H1B in CAP 2020 and it was picked and approved.
Few weeks ago, my client reached out to me and said that they would be firing my Vendor end of September 2019, and would like to retain me but through a different vendor. So, now that my H1b is approved, my client wants me to initiate the transfer to this new vendor as soon as possible.
My OPT Will Also End on End of September
Mine was COS - Change of status, so my H1b would be starting from October 2019.

My question is,
How soon can I initiate my transfer process ?
Can I transfer before October ?
Is there any risk involved ?

Any suggestions or help is highly appreciated.

Thank you.

Well, it is highly recommended to wait until October 1st, work for few days or weeks, get pay stubs and then transfer. USCIS lately has been asking, if the candidate had H1B status or not…so, it is recommended to work for few days on H1B and then file for transfer.

In my case, there will be no payroll after October 1st, cause my vendor would be fired at the end of the September.

Any more suggestions ?

Well, I suggest you speak to a qualified attorney and make a decision on how best to handle it.