I received a CP3219A from the IRS. After submitting additional documents, I have now received a CP2000 for the same year with an amount due that is less than what was on the CP3219A. There was also a note on the CP2000 reminding me that the deadline to file a petition has not been extended, meaning if I still intended to file I must do so by the previously stated deadline. I still don't agree with the new amount due proposed on the more recent CP2000 and already responded to that notice with supporting documents. Now, I am not sure if I should still file the petition since after responding to the CP3219A notice, the IRS sent me a CP2000. Any input is greatly appreciated.
If you want to maximally preserve your options, file a Tax Court petition before the due date. Although you may resolve the issue with the IRS before things get much further, this does guarantee an automatic review by the IRS Appeals office.