HSN Code in GST Invoices: When Is 4-Digit or 6-Digit Mandatory

If you file GST returns, you have probably noticed HSN and SAC codes becoming harder to ignore. The government has been tightening reporting requirements steadily since 2021, and getting them wrong now has real consequences.

WHAT IS AN HSN CODE
HSN stands for Harmonised System of Nomenclature. It is a globally standardized system of product classification maintained by the World Customs Organization. Under GST, goods supplies must carry the correct HSN code on the tax invoice, while services use SAC (Services Accounting Code). These codes identify what is being supplied and the applicable GST rate.

HSN CODE MANDATORY IN GST INVOICE: TURNOVER THRESHOLDS
The number of HSN or SAC digits you must report depends on your Aggregate Annual Turnover (AATO) in the previous financial year:
- AATO up to Rs 5 crore: 4-digit HSN or SAC code is mandatory on B2B invoices and in Table 12 of GSTR-1.
- AATO above Rs 5 crore: 6-digit HSN or SAC code is mandatory on all invoices and in Table 12 of GSTR-1 for both B2B and B2C supplies.

For taxpayers with AATO up to Rs 5 crore, B2C HSN reporting in Table 12 remains optional under current GSTN advisory guidelines.

TABLE 12 GSTR-1 HSN RULES
HSN-wise summary reporting in Table 12 of GSTR-1 became mandatory from 1 April 2021, following Notification No. 78/2020-Central Tax dated 15 October 2020.

From the May 2025 return period, the GSTN introduced Phase 3 changes to Table 12 of GSTR-1 and GSTR-1A. Under Phase 3, manual entry of HSN codes is no longer allowed. Taxpayers must select HSN codes from a dropdown menu, and descriptions auto-populate from the HSN master.

CONSEQUENCES OF WRONG OR MISSING HSN CODES
- Input tax credit disputes where the recipient questions the supply classification
- E-invoice validation failure at the IRP, blocking invoice generation
- Penalty up to Rs 25,000 under Section 125 of the CGST Act for furnishing incorrect information
- GSTR-1 filing errors since the system now validates HSN codes against the master database

HOW TO FIND THE CORRECT HSN CODE
The GST portal at gst.gov.in provides an HSN search tool available both pre-login and post-login. You can search by product description or browse the chapter-wise HSN directory. Always cross-check the HSN code with the corresponding GST rate notification.

PRACTICAL TIP
If you deal in multiple product lines, maintain an internal HSN and SAC mapping sheet with the correct 4 or 6 digit code for each item. Review it at the start of every financial year when your turnover slab may change.