Offer negotiation for L35 Consultant – Deloitte USI

I’ve recently received an offer for an L35 Consultant role at Deloitte USI. My current fixed compensation was around 13 LPA, and the new offer is in the ~20 LPA range.

I’m aiming to push the base to around 22 LPA. My background verification is currently in progress and my joining is scheduled towards the end of September.

I wanted to understand:

Is it realistic to negotiate at this stage (post-offer, during BGV)?

Has anyone successfully negotiated after accepting the initial offer?

What would be the best approach to do this without creating a negative impression?

I have around 3 years of experience.

Would appreciate any guidance from people who have been in a similar situation.