Join's - Teste para não retornar...

Pessoal,Tenho o seguinte SELECT:SELECT T0.DueDate As 'DataVencto', T0.RefDate As 'DataLancto', 'Atraso' = Case When datediff(day,T0.DueDate,GetDate()) > 0 Then datediff(day,T0.DueDate,GetDate()) Else 0 End, T0.Account As 'Titulo', T3.CardName As 'NomeCliente', T0.Credit As 'TotalDoc', T5.CashSum As 'TotalPago', T1.Number As 'DocEntry', T5.TAXDATEFROM JDT1 T0 INNER JOIN OJDT T1 ON T0.TransId = T1.TransId INNER JOIN OACT T2 ON T0.Account = T2.AcctCode INNER JOIN OCRD T3 ON T0.Shortname = T3.CardCode LEFT JOIN RCT2 T4 INNER JOIN ORCT T5 ON T5.DocNum = T4.DocNum ON T4.DocEntry = T1.NumberWhere T3.Cardtype <> 'S' order by T0.duedatePorém, preciso que este select me retorne apenas o que não existe na tabela ORCT.Tentei colocar um Where ORCT.TaxDAte = Null, porém não me retornou nada...O Que tenho que fazer?