Safe harbour option procedure requires timely filing of Form No. 3CEFC and permits invalidation for incorrect or concealed facts. Procedure for exercising the safe harbour option requires the assessee to furnish Form No. 3CEFC to the Assessing Officer before filing the return of income for the relevant previous year. If the option is not exercised, income from the eligible business is determined under the Act without regard to rule 10TIA. The Assessing Officer may declare the option invalid by written order where incorrect facts were furnished or business facts were concealed, after giving a reasonable opportunity of being heard and serving a copy of the order on the assessee.