On December 29, 2021, the Tax Court issued a Memorandum Opinion in the case of Whistleblower 15977-18W v. Commissioner (T.C. Memo. 2021-143). The primary issue presented in Whistleblower 15977-18W was whether the IRS’s Whistleblower Office (WBO) abused its discretion in concluding that the whistleblower claim did not provide specific and credible information sufficient to establish that the target taxpayer was citizen of United States at birth. Held: Discretion sound—no abuse here. Background In early September 2017 the WBO received the petitioner's Form 211. The petitioner provided information to the WBO attempting to show that a certain individual (target) was a dual citizen of the United States and Country X and was subject to, but failed to pay, substantial amounts of various Federal taxes. In support of that claim, the petitioner provided a copy of the target's birth certificate showing that the target was born in the United States, information about…