SQL Server 2014 :: Selecting Records Based On Date

So let's say I have a table Orders with columns: Order# and ReceiptDate. Order#'s may be duplicated (Could have same Order# with different ReceiptDate). I want to select Order#'s that go back 6 months from the last ReceiptDate for each Order#.

I can't just do something like:
SELECT *
FROM Orders
WHERE ReceiptDate >= add_months(date,-6)

because there could be Order#'s whose last ReceiptDate was earlier than 6 months ago. I want to capture all of the instances of each Order# going back 6 months from each last ReceiptDate relative to each Order#.