Rectification of mistake: authority may amend tax orders and intimations, requiring notice and opportunity to be heard before increasing liability. Section 287 authorises specified income-tax authorities to amend orders and intimations to rectify mistakes apparent from the record, either on their own motion or when informed by the assessee, deductor, collector or Assessing Officer, except as respects matters already decided in appeal or revision. Amendments that increase liability require prior notice and a reasonable opportunity to be heard; amendments must be made in writing. Reduced assessments trigger refunds by the Assessing Officer, and increased assessments trigger a prescribed notice of demand. Rectifications are subject to a statutory limitation and a prescribed period for passing orders on applications for amendment.