No later than 45 days after the end of the semiannual period beginning on the first day of each January and the first day of July of each year in which a registrant is registered under section
1603 of this title, each registrant shall file a report with the Secretary of the Senate and the Clerk of the House of Representatives on its lobbying activities during such semiannual period. A separate report shall be filed for each client of the registrant.