Rev. Rul. 2023-8, page 801.

This revenue ruling obsoletes Revenue Ruling 58-74, 1958-1 C.B. 148, relating to the deductibility of research or experimental expenditures for prior taxable years to which the expense method is applicable, because there are insufficient facts in Revenue Ruling 58-74 to properly analyze whether the taxpayer’s failure to deduct certain research or experimental expenditures, when it deducted other research or experimental expenditures, constituted a method of accounting or an error.