According to the American Internal Revenue Service (IRS), the star has neglected to pay $538 858 in taxes to the government.
The Batman Forever star was notified of his debt on July 15.
Kilmer, 49, will be back to work soon, so he should be able to pay his bills. He is on board for the film Silver Cord, which is currently in pre-production, but filming should begin soon in Atlanta, before moving to Canada.