At any time withm four years from the date of any order p.ssed by It the prescribed' authority or the arpellate authority or there isional authority may, on its own motion, rectify any mistake apparen1from the record and shall, within a like period, rectify any such mist:Ike which has been brought to the notice of the prescribed authority o· the appellate authonty or the revisional authority, as the case may b:, by a landholder or other person liable to pay tax:
Provided that no suc1 rectification shall be made which has the effect of enhancing the tax payable unless the landholder and any other person liable to pay tax have been given a reasonable opportunity of being heard in the matter.
• • • \ ~ I I \ ' 240 19 Sa . N hi . \ . omgs ·- ot ng m~ Act shall- ( a) affect the condi 5 of any agreement, g1ant or deed relating to any· d except to the extent herem befoiT.
provided; ~
(b) affect any rights 1ch have accrued to the Government before the date on 'ch this Act comes into force.