anwhathasalreadybeenpaid,thetaxpayermustpaythedifferencetotheIRS.eispartiallyderivedfromgratuitiesleftbycustomershasledtodisputeswiththeIRSandemployersoverhowmuchtheyshouldcontributeinfederalinsurancecontributionact(fica)taxes.Althoughcustomerspaythesetipsdirectlytoemployees,federallawdeemsthetipstohavebeenwagespaidbytheemployerforFICAtaxpurposes.Employersareimputedtohavepaidlargesumsofmoneytheyneverhandledandforwhichtheynowayofascertainingtheexactamount.TheSupremeCourt,in UnitedStatesv.FiorD'Italia,536U.S.238,122S.Ct.2117,153L.Ed.2d280(2002),upheldtheIRS"aggregatemethod"e.InsteadofrequiringtheIRStomakeindividualdeterminationsofunreportedtipsforeachemployeewhencalculatingFICAtax,e.emonthlyonaform.TheIRSthenusesthesetwopiecesofinformationtocalculatewhattheemployerneedstocontributeinFICAtax.