In official Monopoly rules, what happens if a player declines to buy an unowned property?

If a player declines to buy an unowned property in official Monopoly rules, the property is auctioned by the bank.

The player who landed on the property may participate in the auction, and the other players may bid as well. The bank acts as auctioneer, and the property can be sold for any amount that players are willing to offer, including less than its printed purchase price.

Many casual games skip this auction and simply leave the property unowned. That practice changes the pace and strategy of the game, because fewer properties enter circulation and players have fewer opportunities to complete color groups.

The auction rule is one of the most commonly omitted official rules. It applies to purchasable properties, including streets, railroads, and utilities, when the player who lands there chooses not to buy it.