Example. Corporation M's return for the calendar year 1954 was filed on March 15, 1955, and the tax liability shown thereon was paid in equal installments on March 15, 1955, and June 15, 1955. M filed a statement on December 15, 1955, showing the increase in its tax liability resulting from the repeal of sections 452 and 462 and paid at that time the increase in tax shown thereon. No interest will be imposed with respect to the amount of such payment.
Interest shall be computed under the applicable provisions of the internal revenue laws on any portion of the increase in tax shown on the statement which is due after December 15, 1955, and which is not paid when due.
26 C.F.R. §1.9000-6