Access IIF to SQL Statement convert

Question

I have access query and I am converting it to SQL Server 2008R2. I'm looking for the equivalent to the Access IIF statement in SQL Server. Below is the statement I am trying to convert;         ("select IIF(MAX(bill_bno) IS NULL,1,MAX(bill_bno)+1) from rec_all where rw=0 and iif(month(bill_date)>=1 AND month(bill_date)<=3,year(bill_date)-1,year(bill_date))=" & IIf(Month(Date) >= 1 And Month(Date) <= 3, Year(Date) - 1, Year(Date)))