The Cook County treasurer’s office unveils a massive list of properties this weekend ahead of a May auction for investors to buy unpaid property taxes from delinquent property owners.

A partial list of the more than 52,000 properties is being released in Sunday’s Chicago Sun-Times to notify property owners they could lose their land and buildings if they don’t pay their taxes.

More than $186 million in taxes went unpaid a year ago by owners of residential and commercial properties and lots, according to Cook County Treasurer Maria Pappas.

Pappas says fewer properties — amounting to $66 million less in taxes — are expected to be included in the delinquent-tax sale this year than a year ago “because of the tremendous outreach. We’ve located owners, and they’ve come forward.”

About half of the delinquent properties are in Chicago and half in the suburbs.

To purchase unpaid taxes, potential investors need to register between March 9 and April 24 at to participate in the auction. Or they can call the treasurer’s office toll-free at (877) 361-7325. The auction will be May 4-9.

The tax auction works like this: Investors bid a percentage on a property’s taxes, with the lowest percentage winning the auction. From the date of sale, a successful bid earns the buyer that percentage of the still-unpaid taxes every six months.

A successful bid also means the buyer pays the full amount of the unpaid taxes at the time of the sale. After that, it’s up to the tax buyer to watch for any further delinquencies on the property.

A buyer can pay the taxes for subsequent years if the owner again is delinquent.