Recovery of duties: amended procedure sets time limits, voluntary payment mechanism, and penalty for collusion or misstatement. The amended section provides a recovery regime for non-levy, short-levy, erroneous refunds and unpaid interest, allowing voluntary payment before notice which, when notified, precludes subsequent notice or penalty for the paid amount; if the payment falls short the proper officer may issue notice for the shortfall, computing limitation from receipt of the payment information. It distinguishes ordinary cases (one year limitation) from cases involving collusion, wilful misstatement or suppression (five year limitation) and prescribes procedural timelines and definitions for the relevant date.