HSN code disclosure requirement on tax invoices varies by turnover threshold under UTGST notification, effective from the commencement date. Notification prescribes digit-wise disclosure of the Harmonised System of Nomenclature (HSN) codes on tax invoices for registered persons under UTGST, mapping specified annual turnover bands to required numbers of HSN digits (nil, two, or four). The requirement is issued under the first proviso to rule 46 of the UTGST Rules, on the GST Council's recommendation, and comes into force on the stated commencement date.