as may be required by the regulations in this subpart and by the instructions relating to the return.” (emphasis added)). 24 . Id. § 31.6205-l(a)(4). 25 . The final paragraph of Revenue Ruling 75-464 identifies two exceptions to interest-free treatment that equate ascertainment of error with the conclusion of an appeals process: (1) "cases in which the taxpayer’s returns for prior years were audited and additional tax found to be due with respect to the same issue involved in the current audit”; and (2) "cases in which the taxpayer, after having been informed of his tax status as an employer, knowingly underreports his employment tax liability in subsequent years.” Rev. Rul. 75-464, 1975-2 C.B. 474; see also Atchison, Topeka & Santa Fe Ry. Co. v. United States, 61 Fed.Cl. 84, 89 (2004) (<HOLDING>). 26 . As previously noted, the IRS’s three
holding that revenue ruling 75464 appears to treat ascertainment of the error as synonymous with the conclusion of the administrative appeals process but in no event later than receipt of notice and demand the tax payment is thus interestfree if the tax is paid at the conclusion of administrative appeals but prior to filing a refund claim and prior to the irs issuing a notice and demand holding notice of balance due satisfies notice and demand requirements holding that a refund may include additional taxes paid after the filing of a refund claim so long as the total does not exceed the portion of tax paid prior to the administrative claim holding that a ruling of the trial court to which no error has been assigned becomes the law of the case and is not subject to review by the court of appeals holding that a tax refund claim must be dismissed if the principal tax deficiency has not been paid in full