error in if statement

[learner03]

How can I rectify this error-

MaxNewDate = var SO= Retail_Backorder[Simba Ref#]

var ifT=Maxx(Filter(All(Retail_Backorder),Retail_Backorder[Simba Ref#]=SO),Retail_Backorder[Est. Delivery Date])

var NewDate=if(Retail_Backorder[Est. Deliv Date]="",Retail_Backorder[Est. Deliv Date],if(LEN(Retail_Backorder[Est. Deliv Date])>0||Retail_Backorder[Ship Complete]="T",ifT,Retail_Backorder[Est. Deliv Date]))

return

NewDate

[ryan_mayu · Accepted solution]

@learner03 

maybe try to change 

Retail_Backorder[Est. Deliv Date]=""

to

ISBLANK(Retail_Backorder[Est. Deliv Date])