HSN code disclosure requirement: turnover-linked invoice obligations require specified HSN digit disclosure on tax invoices. Notification prescribes mandatory disclosure of Harmonised System of Nomenclature (HSN) code digits on tax invoices by registered persons linked to their annual turnover in the preceding financial year, dividing taxpayers into three turnover bands with corresponding requirements: nil for the lowest band, two digits for the middle band, and four digits for the highest band under rule 46 of the Kerala GST Rules, 2017.