((a)) ** Entities covered by ** A person, other than a lobbying firm, that is required to report and does report lobbying expenditures pursuant to may—
((1)) make a good faith estimate (by category of dollar value) of applicable amounts that would be required to be disclosed under such section for the appropriate quarterly period to meet the requirements of sections 1603(a)(3) and 1604(b)(4) of this title; and
((2)) for all other purposes consider as lobbying contacts and lobbying activities only—
((A)) lobbying contacts with covered legislative branch officials (as defined in ) and lobbying activities in support of such contacts; and
((B)) lobbying of Federal executive branch officials to the extent that such activities are influencing legislation as defined in .
((b)) ** Entities covered by ** A person, other than a lobbying firm, who is required to account and does account for lobbying expenditures pursuant to may—
((1)) make a good faith estimate (by category of dollar value) of applicable amounts that would not be deductible pursuant to such section for the appropriate quarterly period to meet the requirements of sections 1603(a)(3) and 1604(b)(4) of this title; and
((2)) for all other purposes consider as lobbying contacts and lobbying activities only—
((A)) lobbying contacts with covered legislative branch officials (as defined in ) and lobbying activities in support of such contacts; and
((B)) lobbying of Federal executive branch officials to the extent that amounts paid or costs incurred in connection with such activities are not deductible pursuant to .
((c)) ** Disclosure of estimate** Any registrant that elects to make estimates required by this chapter under the procedures authorized by subsection (a) or (b) for reporting or threshold purposes shall—
((1)) inform the Secretary of the Senate and the Clerk of the House of Representatives that the registrant has elected to make its estimates under such procedures; and
((2)) make all such estimates, in a given calendar year, under such procedures.
((d)) ** Study** Not later than , the Comptroller General of the United States shall review reporting by registrants under subsections (a) and (b) and report to the Congress—
((1)) the differences between the definition of “lobbying activities” in and the definitions of “lobbying expenditures”, “influencing legislation”, and related terms in sections 162(e) and 4911 of title 26, as each are implemented by regulations;
((2)) the impact that any such differences may have on filing and reporting under this chapter pursuant to this subsection; and
((3)) any changes to this chapter or to the appropriate sections of title 26 that the Comptroller General may recommend to harmonize the definitions.