Whenever the Board finds at any time that the balance in the railroad unemployment insurance account will be insufficient to pay the benefits and refunds which it estimates are due, or will become due, under this chapter, it shall request the Secretary of the Treasury to transfer from the Railroad Retirement Account to the credit of the railroad unemployment insurance account such moneys as the Board estimates would be necessary for the payment of such benefits and refunds, and the Secretary shall make such transfer. Whenever the Board finds that the balance in the railroad unemployment insurance account, without regard to the amounts transferred pursuant to the next preceding sentence, is sufficient to pay such benefits and refunds, it shall request the Secretary of the Treasury to retransfer from the railroad unemployment insurance account to the credit of the Railroad Retirement Account such moneys as in its judgment are not needed for the payment of such benefits and refunds, plus interest at a rate for each fiscal year equal to the average rate of interest borne by all special obligations held by the Railroad Retirement Account on the last day of the preceding fiscal year, rounded to the nearest multiple of one-eighth of 1 per centum, and the Secretary shall make such retransfer. In determining the balance in the railroad unemployment insurance account as of September 30 of any year pursuant to section
358
(a) of this title, any moneys transferred from the Railroad Retirement Account to the credit of the railroad unemployment insurance account which have not been retransferred as of such date from the latter account to the credit of the former, plus the interest accrued thereon to that date, shall be disregarded.