The U.S. Postal Service states that a child may simply address their letter to Santa Claus, North Pole. This is part of the guidelines for the Postal Service's "Operation Santa/Letters to Santa" program.
The U.S. Postal Service has been responding to letters from children to Santa Claus since 1912. The current process allows children to receive a letter postmarked from the North Pole with a reply from Santa. A parent simply takes the letter their child has written and addressed to the North Pole and places it in an envelope addressed to the Anchorage Postmaster. The post office also provides volunteer gift givers the opportunity to provide gifts to underprivileged children through these letters.