law: 10. Power of Board to issue directions, etc.-
  (1) The Central Board of Direct Taxes may, from time to time, issue such directions or orders to the income-tax authorities, as it may deem fit: Provided that no direction or order shall be issued so as to require any designated authority to dispose of a particular case in a particular manner.
  (2) Without prejudice to the generality of the foregoing power, the said Board may, if it considers necessary or expedient so to do, for the purpose of this Act, including collection of revenue, issue from time to time, general or special orders in respect of any class of cases, setting forth directions or instructions as to the guidelines, principles or procedures to be followed by the authorities in any work relating to this Act, including collection of revenue and issue such order, if the Board is of the opinion that it is necessary in the public interest so to do.