Minn. Stat. § 281.326: CANCELLATION OF CERTIFICATES WHEN NOTICE OF EXPIRATION OF TIME FOR REDEMPTION NOT GIVEN WITHIN SIX YEARS.

The county auditor shall annually, as soon as practicable after the second Monday of May, cancel of record all real estate tax judgment sale certificates, state assignment certificates, and forfeited tax sales certificates upon which notice of expiration of time of redemption has not been given within a period of six years next following the date of the issuance of such certificate, by making an entry in the proper copy real estate tax judgment book, opposite the description of land covered by such certificate, "canceled by limitation."