On September 9, 2021, the Tax Court issued a Memorandum Opinion in the case of Kaebel v. Commissioner (T.C. Memo. 2021-109). The primary issues presented in Kaebel v. Commissioner were (a) whether the petitioner was precluded from arguing that the IRS did not send him deficiency notices; (b) whether the IRS erred in certifying that the petitioner had seriously delinquent tax debt; and (c) whether the petitioner should be sanctioned for advancing the groundless argument that