Payroll aggregating involves an employer combining supplemental wages with regular wages and withholding the total as if it were a single payment for the regular pay period.

The Federal Circuit, affirming the Court of Federal Claims, has held that for purposes of calculating the FICA contribution and benefit wage base and the FUTA wage base, a payroll service company couldn't aggregate wages paid to workers who performed services during the year for several of its clients (Cencast Services L.P., (CA-FC 9/10/2013) 112 AFTR)