Is it legal to bill insurances different amounts for the same CPT code

[newprivatepractice]

Hi

I am trying to understand how a sliding scale works with being an out of network provider.  If I know the maximum reimbursement rate for client X's policy at Aetna is 400 and for client Y's policy at Aetna is 250.  Is it legal to charge client X 400 and client Y 250?  Or do I have to charge both clients the same amount across the board?

Thanks for any input

[Michele]

If you are out of network, why are you concerned with what the insurance allows?  Not really needed to answer the question, but I am curious.  You should have one set fee schedule across the board.  Usually a sliding scale is set up for self pay patients based on their income.  The sliding scale wouldn't be set up based on what the insurance carrier allows.