What is Certificate Of Purchase?

Legal Definition
A certificate issued by the proper public officer to the successful bidder at a judicial sale (such as a tax sale) setting forth the fact and details of his purchase, and which will entitle him to receive a deed upon confirmation of the sale by the court, or (as the case may bs) if the land is not redeemed within the time limited for that purpose. Lightcap v. Bradley, 186 111 510, 58 N. E. 221; Taylor v. Weston, 77 Cal. 534, 20 Pac. 62.
-- Black's Law Dictionary