Penalty waiver power: discretionary reduction or waiver allowed for voluntary full disclosure and cooperation, subject to procedural safeguards. Principal Commissioners or Commissioners may discretionarily reduce or waive penalties under section 439 where the taxpayer made a full and true voluntary disclosure before detection, cooperated with assessment enquiries, and paid or arranged to pay tax or interest. A disclosure is deemed full if the assessed-returned difference does not attract penalties. Multi-year waiver exceeding the high-value threshold and larger aggregate concessions require prior higher-authority approval. Applications invoking genuine hardship may permit reduction, waiver, stay or compounding, must be decided within twelve months, and cannot be rejected without a hearing. Orders under the section are final and not open to challenge.