26 CFR § 1.669(b)-2 - Manner of exercising election.
(a) By whom election is to be made. Except as otherwise provided in this paragraph, a taxpayer whose tax liability is affected by the election shall make the election provided in section 669(a). In the case of a partnership, or a corporation electing under the provisions of subchapter S, chapter 1 of the Code, the election shall be exercised by the partnership or such corporation.
(b) Time and manner of making election. The election under section 669(a) may be made, or revoked, at any time before the expiration of the period provided in section 6501 for assessment of the tax. If an election is revoked, a new election may be made at any time before the expiration of such period. The election (or a revocation of an election) may be made in a letter addressed to the district director of internal revenue for the district in which the taxpayer files his tax return (or the Director of International Operations where appropriate) or may be made in a statement attached to the return. In any case where all the information described in § 1.669(b)-1 is not furnished at or before the time the beneficiary signifies his intention of making an election and by reason thereof an election has not been made, and subsequent thereto, but before the expiration of the period provided in section 6501 for the assessment of the tax, there is furnished the required information not previously furnished, the election will be considered as made at the time such additional information is furnished.