603. Where a taxpayer who was a member of a partnership during a fiscal period has, for the purpose of computing the taxpayer’s income from the partnership for the fiscal period, entered into an agreement or made an election, a designation or a specification under the regulations made under section 104, under any of sections 96, 119.15, 156, 180 to 182, 230, 279, 280.3, 299, 485.6, 485.9 to 485.11, 485.42 to 485.52, 614, 832.23 and 832.24 or, because of subparagraph a of the second paragraph of section 614, under the first paragraph of section 522 that, but for this section, would be a valid agreement, designation, specification or election, as the case may be, the following rules apply:(a) the agreement, designation, specification or election is not valid unless it was entered into or made on behalf of the taxpayer and each other member of the partnership during the fiscal period and the taxpayer had authority to act for the partnership;
(b) if the agreement, designation, specification or election is valid under paragraph a, each other member of the partnership during the fiscal period is deemed to have entered into the agreement or made the designation, specification or election, as the case may be; and
(c) despite paragraph a, any agreement, designation, specification or election deemed to have been entered into or made, as the case may be, by a member under paragraph b is deemed to be a valid agreement, designation, specification or election entered into or made by that member.