Credit and debit notes: rules for issuance, reporting deadlines and tax adjustment under the GST framework. Section 34 requires suppliers to issue credit notes when an invoice overstates taxable value or tax, goods are returned, or supplies are deficient, and to declare such credit notes in the return for the month of issuance or by the following September/annual return deadline; reductions in output tax are barred if tax incidence and interest were passed to another person. It requires suppliers to issue debit notes where an invoice understates taxable value or tax, declare them in the return for the month of issuance, and adjust tax liability; 'debit note' includes a supplementary invoice.