No one wants to hear that their catalytic converter needs to be replaced, since it is common for the job to cost over $1000. But this is a case in which a little bit of research can result in the car manufacturer picking up the tab.
First, some background. Your car does not burn fuel completely during the combustion process. It is the job of the emissions system to process the remnants of that fuel that escape through the exhaust to the environment. By way of the emissions system, harmful pollutants like carbon monoxide, hydrocarbons and nitrogen oxide are converted into more manageable substances like carbon dioxide, water vapor, nitrogen and oxygen.
A cast of characters in your emissions system plays a part in cleaning up your car's exhaust. Support roles are played by parts with names like EGR valve and oxygen sensor, but there are three stars: the catalytic converter, the electronic emissions control unit (ECU) and the onboard emissions diagnostic device (OBD).
The reason they receive top billing is that they are considered major components of the emissions system--and because of that, there is a federally mandated requirement that the car companies stand behind these parts for eight years or 80,000 miles. This is above and beyond whatever warranty your car came with and covers all the owners of the vehicle.
Your owner's manual contains information about the emissions warranty; there may be a requirement that the maintenance schedule be followed. There is also a requirement that a service facility replacing a catalytic converter have you sign off on the fact that your vehicle is beyond the eight-year, 80,000-mile window for coverage under the federally required warranty. This protects you against a shop billing you for a job that would otherwise be paid for by the car manufacturer.
The EPA's fact sheet on the subject outlines the procedure you should follow if you think your car needs emissions repairs under the mandate: