Hi Safeer,
Try this Qurery
Select Top 10 B.CardCode,Max(B.Cardname),DATEDIFF(DD,C.DocDueDate,B.DocDate) as 'No. Of Days'
from RCT2 A inner join ORCT B on A.DocNum=B.DocEntry
Inner Join OINV C on C.DocEntry=A.DocEntry and A.InvType=13
Group by B.CardCode,C.DocDueDate,B.DocDate
Order By DATEDIFF(DD,C.DocDueDate,B.DocDate)