(6) Where the assessee is a person other than a company or a co-operative society, no deduction shall be admissible under sub-section (1) unless the accounts of the assessee for the year or years in which the expenditure specified in sub-section (2) is incurred have been audited by an accountant as defined in the Explanation below sub-section (2) of section 288, and the assessee furnishes, along w