Audit Engagements

Is it proper protocol to have the Supervisory Committee sign for any and all external audits requested/completed?  We're in the midst of establishing an internal audit function and the in the past the supervisor of EFT/ACH has always signed for the ACH Audit.  I feel like this is something that the Supervisory Committee should be over and should actually sign for.  Would I be correct in thinking this?  I did notice that it is called a Risk and Compliance Services Agreement and not an actual Engagement Letter.  Any suggestions/input would be appreciated.  Thank you!