base period T-bill rate

For purposes of this subsection, the term “base period T-bill rate” means the annual rate of interest determined by the Secretary to be equivalent to the average investment yield of United States Treasury bills with maturities of 52 weeks which were auctioned during the 1-year period ending on September 30 of the calendar year ending with (or of the most recent calendar year ending before) the close of the taxable year of the shareholder.

For purposes of this subsection, the term “base period T-bill rate” means the annual rate of interest determined by the Secretary to be equivalent to the average of the 1-year constant maturity Treasury yields, as published by the Board of Governors of the Federal Reserve System, for the 1-year period ending on September 30 of the calendar year ending with (or of the most recent calendar year ending before) the close of the taxable year of the shareholder.