are you looking at top 5 values for each year?
then use
SELECT *
FROM
(
SELECT ROW_NUMBER() OVER (PARTITION BY YEAR(Table_PurchaseOrder_Information.CreatedDate) ORDER BY Table_PurchaseOrder_Information.CreatedDate DESC) AS Seq,
Table_PurchaseOrder_Information.PO_Number, Table_PurchaseOrder_Information.Supplier, Table_PurchaseOrder_List.Unit_Price,
Table_PurchaseOrder_Information.CreatedDate
FROM Table_PurchaseOrder_Information INNER JOIN
Table_PurchaseOrder_List ON Table_PurchaseOrder_Information.ReferenceNumber = Table_PurchaseOrder_List.ReferenceNumber
)t
WHERE Seq<=5
ORDER BY CreatedDate DESC
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SQL Server MVP
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