(a) Declared value excess-profits tax. Gain which is includible in gross income under § 287.23 shall be included in gross income for all income and excess-profits tax purposes, but not for the purposes of the declared value excess-profits tax and the capital stock tax as provided in section 511(i) of the Act. In lieu of any adjustment with respect to such declared value excess-profits tax, there is imposed for any taxable year ending on or before June 30, 1945, in which the gain is realized an additional tax of 1.1 percent of the amount of the gain. No additional capital stock tax liability is incurred.

(b) Improper deposits. In the case of deposits in the construction reserve fund of amounts derived from sources other than those specified in section 511 of the Act, or in the case of failure to deposit an amount equal to the “net proceeds” or “net indemnity” within the period prescribed in section 511(c) of the Act and § 287.15, the taxpayer obtains no suspension or postponement of any tax liability and the tax is collectible without regard to the provisions of section 511(c) of the Act.

(c) Time for filing claim subsequent to election under section 511(c)(2). If an election is made under section 511(c)(2) of the Act, and paragraph (a)(2) of § 287.12, and if computation or recomputation in accordance therewith is otherwise allowable but is prevented, on the date of filing of notice of such election, or within six months thereafter, by any statute of limitation, such computation or recomputation nevertheless shall be made notwithstanding such statute if a claim therefor is filed within six months after the date of making such election. If as the result of such computation or recomputation an overpayment is disclosed, a claim for refund on Form 843 should also be filed within such six months' period.