Amortisation of preliminary expenses permits approval of outside consultancies for feasibility and project work under specified eligibility rules. Amortisation under Section 35D allows qualifying preliminary expenses-including feasibility and project reports, market or other surveys, and engineering services-to be written off in ten equal instalments when work is done in house, by the assessee, or by an outside consultancy concern approved by the Central Board of Direct Taxes. The Board's approval guidelines require competence and experience in consultancy services, ordinarily Indian residence, at least one year of prior activity with fees from a client, and an income tax clearance certificate; applications must supply specified particulars and supporting information.