Code of Federal Regulations Title 26. Internal Revenue § 26.1.165–4 Decline in value of stock

(b) Stock owned by banks.(1) In the regulation of banks and certain other corporations, Federal and State authorities may require that stock owned by such organizations be charged off as worthless or written down to a nominal value. If, in any such case, this requirement is premised upon the worthlessness of the stock, the charging off or writing down will be considered prima facie evidence of worthlessness for purposes of section 165(a);  but, if the charging off or writing down is due to a fluctuation in the market price of the stock or if no reasonable attempt to determine the worthlessness of the stock has been made, then no deduction shall be allowed under section 165(a) for the amount so charged off or written down.

(2) This paragraph shall not be construed, however, to permit a deduction under section 165(a) unless the stock owned by the bank or other corporation actually becomes worthless in the taxable year. Such a taxpayer owning stock which becomes worthless during the taxable year is not precluded from deducting the loss under section 165(a) merely because, in obedience to the specific orders or general policy of such supervisory authorities, the value of the stock is written down to a nominal amount instead of being charged off completely.