Consequences of rejecting offer 2 days before joining

I'm in talks with a startup, but they want immediate joiners so my joining date is next Wed. Anyways I just want this offer to negotiate with another company. They'll be releasing offer by Friday & I will reject it on Monday

But want to understand is there any consequences. Like putting entry in EPFO portal even through i didn't joined them & i might get double entry there

Should I take this risk? Never done like this before They've all my details like PAN, Aadhar, bank account number etc