HSN code disclosure requirement: invoices must state prescribed digit length based on annual turnover tiers. Notification requires registered persons to include Harmonised System of Nomenclature (HSN) code digits on tax invoices according to turnover-based tiers: the lowest turnover tier is exempt, the intermediate tier must state two digits, and the highest tier must state four digits; the requirement applies from the notified commencement date under the first proviso to rule 46 of the Nagaland GST Rules, 2017.