Rectification of mistake: authority to amend tax orders for apparent errors, subject to notice and hearing rights. Assessing Officers may amend orders to rectify apparent mistakes within one year from the end of the financial year of the order; amendments may be suo moto or on the assessee's notice but cannot alter matters already decided on appeal. Amendments increasing liability require notice and a reasonable opportunity of being heard and must be made by written order. Reducing assessments triggers refunds; enhancing assessments or reducing prior refunds requires an order specifying sums payable and application of the Chapter's collection provisions.