As per RULE LINK – Rule 26C of the Income Tax Rules – Form No. 12BB is required to be furnished by an employ​ee to his employer for estimating his income or computing the tax deduction at source. An assessee shall furnish evidence or particulars of the claims, such as House Rent Allowance, Leave Travel concession, Deduction of Interest under the head ” Income from house property” and deductions under Chapter-VIA in Form No. 12BB​ for estimating his income or computing the tax deduction at source.