Commissions paid to client's benefits administrator: Contra Revenue or Expense?

I've searched around for an answer to this but can't find any guidance that translates to my exact situation below: Provider ABC provides services and wishes to make an arrangement with Company XYZ. These services are in the benefits variety and Company XYZ does not internally manage its own benefits package that it provides to its employees, so it sends Provider ABC to its 3rd party benefits administrator to broker a deal. Benefits Administrator requires that Provider ABC pay commissions of 5% of the monthly fees it collects from Company XYZ for the services that it provides in exchange for brokering the deal that allows Provider ABC to enter into the arrangement with Company XYZ. All parties agree and Provider ABC enters into two contractual agreements: 1) The provider agreement with Company XYZ that stipulates services provided and price, 2) The agreement with the Benefits Administrator that stipulates the commissions it will pay of the monthly fees it collects from Company XYZ. Is the proper accounting for Provider ABC to record the 5% commissions it pays to Benefits Administrator as contra-revenue (recognizing only the remaining 95% net revenue), a cost of services provided (COGS), or SG&A expense? Any GAAP references that support your answer would be appreciated as well.