H1B Transfer

Hi,

Hope your well.

I applied for H1B through Employer A and visa is valid from Aug 2017 till Sep 2019.

Now I got better offer with Employer B.

Please note i did not enter into US yet and I don’t have SSN, paystubs of US employer etc

I would like to know, can I transfer my H1B to Employer B on day 1 of my visit to US without SSN, Paystubs of US Employer?.