If you've got a crumpled old Lotto ticket in your wallet, you could be sitting on a pile of unclaimed cash.

The winner of last weekend's $16.2 million Lotto Powerball prize has yet to come forward - and their fortune is not the only unclaimed prize.

The lucky ticket, sold at Countdown Hamilton, is among four major prizes which haven't yet been cashed.

The other three are a two million dollar prize from a ticket sold at Christchurch's Fresh Choice Barrington in November, a one million dollar ticket bought from Glenfield's Pam's Corner Dairy in September, and a 100 thousand dollar Keno win from a Pak'nSave Mangere ticket in July.

Lotto tickets are valid for 12 months.