JOIN type for MS-Access report query
This seems to have worked:

SELECT SLD.SLD_Number, SLD.Date_Received, SLD.Time_Received, [Payment 
table].Date_Received, IIf(Payment_Status='NOT PAID',DateDiff("d",[Invoice 
table].Date_Received,Date())) AS Expr1, 
IIf(Payment_Status='PENDING',DateDiff("d",[Invoice 
table].Date_Received,Date())) AS Expr2, DateDiff("d",[Invoice 
table].Date_Received,[Payment table].Date_To_Payment) AS Expr3, 
DateDiff("d",[Order table].Date_Quotes_Requested,SLD.Date_Received) AS 
Expr4, DateDiff("d",[Order table].Date_Of_Order_Number,SLD.Date_Received) AS 
Expr5, IIf(Payment_Status='PAID',DateDiff("d",[Invoice table].Date_Received,
[Payment table].Date_Authorised_Paid)) AS Expr6, IIf([Invoice 
table].Date_Received=NULL,'True','No') AS Expr7, 
Format(SLD.Date_Received,"mmm-yyyy") AS [Month Of SLD]
FROM (([Payment table] RIGHT OUTER JOIN SLD ON SLD.SLD_ID = [Payment 
table].SLD_ID) LEFT OUTER JOIN [Order table] ON [Payment table].SLD_ID = 
[Order table].SLD_ID) LEFT OUTER JOIN [Invoice table] ON [Invoice 
table].SLD_ID = [Payment table].SLD_ID;