var cte_company = from t in AccountDB.TblCompanies
                         select new
                         {
                             CompanyID = t.CompanyID,
                             CompanyName = t.CompanyName,
                             CompanyNumber = t.CompanyNumber,
                             IncorporatedDate = t.IncorporatedDate,
                             TOTAL_YEARS = new DateTime((DateTime.Now - t.IncorporatedDate).Ticks).Year - 1
                         };
            var TaxReturnDate = AccountDB.TblTaxes.MaxBy(x => x.HeTaxReturnDate).select(x => x.HeTaxReturnDate).First();
            var result = from tax in AccountDB.TblTaxes
                         join cte in cte_company
                         on cte.CompanyID equals tax.CompanyID
                         select new
                         {
                             cte.CompanyID,
                             cte.CompanyName,
                             cte.CompanyNumber,
                             cte.IncorporatedDate,
                             cte.TOTAL_YEARS,
                             TaxDate =(DateTime) (cte.TOTAL_YEARS > 1 ? TaxReturnDate.AddMonths(9) : cte.TOTAL_YEARS <= 1 ? cte.IncorporatedDate.AddMonths(21))

                         };