Full expression is:
Insp Date: CDate(IIf([RFA MAIN].[PermitExtension]="3 Months",DateAdd("m",13,DateSerial(Year([rfa main].[DATE RET'D TO CUST]),Month([rfa main].[DATE RET'D TO CUST])+1,0)),IIf([RFA MAIN].[PermitExtension]="6 months",DateAdd("m",16,DateSerial(Year([rfa main].[DATE RET'D TO...