Interest on late GST tax is payable only on tax paid via the electronic cash ledger, except where assessment proceedings have begun. The substituted proviso to section 50(1), with retrospective effect from 1 July 2017, provides that interest on tax for supplies declared in a return furnished after the due date is payable only on the portion of tax paid by debiting the electronic cash ledger, except where the return is furnished after the commencement of assessment or adjudication proceedings for that period.