Christie Brinkley is a tax cheat. At least the IRS says she is.

They say she owes $531,000 in back taxes and they just put a lean on her Long Island home in that amount. Not that she should be sweating it. Christie is reportedly worth tens of millions of dollars.

Her rep says, "Christie Brinkley was surprised to hear today that a tax lien had been filed, and has instructed her team to resolve the matter immediately."

The IRS also told Brinkley that she can no longer live in her uptown world...