The Supreme Court has sided with the IRS in a case that involves owing the IRS money, bank records, taxpayer privacy, and notice.
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The IRS does not need to notify third parties when requesting a summons for banking records in collection matters.
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Under the Bank Secrecy Act and the third-party doctrine (upheld in
United States v. Miller, 1976), courts have ruled that individuals have no reasonable expectation of privacy in records held by third parties.
The IRS can issue an administrative summons (26 U.S. Code § 7602) to those third parties to obtain financial records without needing a warrant or showing probable cause. The IRS only needs to show that the records are
relevant to an inquiry - a much lower standard than probable cause.