For background on the process, I cut and paste this (footnotes omitted) from a version of the working draft of my Federal Tax Procedure Book (basically same as in my Federal Tax Procedure 2019 editions):
In an increasingly globalized economy, records relevant to tax administration in one country may be possessed by someone in another country. Under many U.S. bilateral tax treaties, one treaty partner is obligated to assist the other in gathering information relevant to the latter's tax administration. For example, the Canadian tax authority (referred to as the “competent authority” in treaty parlance) under the U.S./Canada Double Tax Treaty may request the U.S. tax authority (i.e., the U.S. competent authority) to obtain information in the U.S. for Canadian tax administration. (This is commonly referred to as an “exchange of information” provision.) If the request is within the scope of the treaty, the U.S. competent authority will authorize the IRS to issue an administrative summons. The ultimate taxpayer involved may then bring a motion to quash if the summons is to a third party or, if the summons is to the taxpayer, may invoke any basis for noncompliance and await the IRS's pursuit of a summons enforcement proceeding.
In United States v. Stuart, 109 S. Ct. 1183 (1989), Canada made such a request to the U.S., the U.S. issued summonses to third parties, and the taxpayer brought a motion to quash. The issue presented was whether the Code's limitation on the use of administrative summonses when a DOJ referral is in effect (§ 7602(d)) applies in the case of a summons issued under the Canadian treaty in relation to the Canadian tax. That Code limitation had been enacted after the U.S./Canadian double tax treaty in question had been negotiated and entered into force. Arguably, even if that limitation were not in the treaty, Congress's subsequent legislation may have created a treaty override. The taxpayer argued that the status of the Canadian tax investigation was the equivalent of a DOJ referral and thus the use of an IRS administrative summons was not proper. The Court held that, notwithstanding the subsequent enactment, the treaty itself controlled and had no such limitation, so that it need not inquire into the status of the Canadian investigation.
In subsequent cases, courts have held that the propriety of the foreign country’s tax investigation is not relevant to whether the IRS can issue and enforce the summons (or avoid a petition to quash the summons); rather, the issue is whether the IRS has met the Powell requirements for the summons focusing on its actions and not that of the foreign treaty partner requesting the IRS to use its processes to obtain the requested information.
Similar processes are available under the OECD Convention on Mutual Assistance in Tax Matters, which is a multilateral treaty, and possibly other treaties as well, although most of the litigated cases appear to involve the bilateral double tax treaties.The process employed in Redfern for the summons as follows (Slip Op. p. 2):
As required by Internal Revenue Code § 7609(a)(1), the IRS provided Redfern, as the holder of the accounts, with notice of the summons and an explanation of the recipient’s right to bring a proceeding to quash the summons. Specifically, it mailed the required notice to Redfern at (1) the address that appeared on his most recently filed and processed federal tax return and (2) the address identified by France as the address he reported to the government, as well as (3) to Leslie R. Kellogg, an attorney at Hodgson Russ LLP, from whom the IRS had received a power of attorney signed by Redfern authorizing her to receive confidential tax information on Redfern’s behalf.
