In GSTR – 1 Harmonized System of Nomenclature for goods (HSN) should be shown mandatorily for exports. HSN is not mandatory for taxable person whose aggregate turnover is less than 1.5 crores. HSN shall be restricted to maximum 8 digits. If gross turnover in the previous financial year is greater than Rs 5 crore, HSN should be a minimum of 4 digits. If gross turnover in the previous financial year is equal to or greater than Rs 1.5 crore and less than Rs 5 crores, HSN should be a minimum of 2 digits and would be mandatory from the second year of GST implementation.