If you don’t, you could miss out on the ability to file a petition with the Tax Court. The IRS sends notices to the last known address (which starts the period of time for filing a petition); receipt of the notices does not control the filing deadline. That’s what one taxpayer learned the hard way. It’s up to taxpayers to tell the IRS if there’s been a move (use Form 8822 for individuals; Form 8822-B for businesses).