Tax deduction and collection account number required for withholding agents; must be quoted in payments, certificates and returns. Every person required to deduct or collect tax must apply to the Assessing Officer for allotment of a tax deduction and collection account number if not already allotted, and must thereafter quote that number in challans for payment, in certificates, in statements and returns required under the law, and in other prescribed documents relating to those transactions; the Central Government may notify exemptions from these requirements.