Rectification of mistake allows amendment of tax orders to correct apparent errors, with notice when liability increases. Rectification permits the tax authority to amend its order to correct an apparent mistake within a limited period, except as regards matters already considered and decided on appeal or revision. The authority may act on its own motion or must amend when a mistake is pointed out by the assessee or, for Commissioner (Appeals), by the Assessing Officer. Amendments increasing liability require prior notice and opportunity to be heard; amendments must be in writing. Refunds must be made where assessment is reduced, and a prescribed notice of demand is issued where assessment is enhanced or a refund reduced.