Is it possible for child support to collect backpayments for payees after having the payer reviewed and if so, what is the legitimate amount of time to be back dated??

I'm not sure what you mean by having the payer reviewed. It can take a long time to collect back support. Has the payor been making any kind of payments at all? How long has it been since the last payment?

Yes but payee saying that earning more than tax assessment and having a review

Where are you located? Is there current support or just back support?

Child support arrears can be collected at any time. In most jurisdictions there is no statute of limitations for back child support.