Furnishing details of inward supplies required within the prescribed monthly return window; unmatched entries must be rectified with tax and interest. Registered persons (with specified exclusions) must electronically furnish and reconcile details of inward supplies, including reverse-charge and integrated-taxable supplies and related credit/debit notes, within the prescribed monthly return window following the tax period; the Commissioner may extend the time. Recipients' modifications must be communicated to suppliers as prescribed. Unmatched entries discovered later must be rectified in the period of discovery with payment of any tax shortfall and interest, subject to a statutory cut-off that ends on the earlier of the September return of the subsequent financial year or the annual return.