The benefits of this act shall extend to and accrue to any successful bidder or purchaser at sheriff's or other judicial sale, grantee, transferee, mortgagee, or other party in interest in the parcel or parcels of real estate against which the above mentioned taxes have been assessed and levied.

For the purposes of this act, a tax shall be deemed to become delinquent on the date of its registry as a delinquent tax or on the fifteenth day of January of the year, following the current year for which the tax in question was levied.