Firm registration under the Income-tax Act requires Form No. 11, benami declaration, and detailed partner profit apportionment. Form No. 11 requires filing an application for firm registration under the Income-tax Act with the Assessing Officer, enclosing the partnership instrument. The applicant must declare no partner was a benamidar in relation to firm shares (except spouse or minor child), and provide a Schedule detailing each partner's name, address, admittance date, interest on capital/loans, remuneration, profit/loss share percentage and remarks, including conditions for payments dependent on profits and notation for partners who share profits but not losses.