Washington D.C. is the capitol of the United States.
The U.S. Constitution states that a special district may be created to permanantly serve as the nations capitol, therefore it does not belong to any state and is overseen directly by the federal government. Auctions happen year round, depending on the type of sale. The Office of Tax and Revenue is responsible for collecting taxes as well as conducting the tax sale auctions.
Auction Process / Redemption:
There are three types of sales that happen in D.C.; Tax Lien Certificate, Special Deed, and Discounted sales. All types adhear to the 'Premium Bid' system in order to win a property at auction. Parcels purchased at the annual lien sale are subject to a 6 month redemption period, where an interest rate of 1.5% is accrued each month.