You have to keep all your business information for six years from the end of the last tax year to which it applies.
If you file a return late, keep all the information for six years from that filing date.
If your corporation dissolves, you have to keep all of its information for two years after the date of dissolution.
Be sure to keep all records that relate to an objection or appeal until the process is finished and the time for filing any further appeals has expired.