What Is an HSN Code? A Simple Guide for Indian Businesses

If you raise GST invoices, you have seen HSN codes — those numbers next to each product. They are not just red tape. Used correctly, they keep your invoices and GST returns clean and consistent. Used carelessly, they invite notices. Here is what every business owner should know.

What is an HSN code?

HSN stands for Harmonized System of Nomenclature — an international system for classifying goods, developed by the World Customs Organization. More than 200 countries use it, which means a product carries the same base code almost everywhere in the world.

India adopted HSN for GST so that every product has a single, uniform classification. The international HSN code is 6 digits. India extends it to 8 digits for finer classification of goods.

Why HSN codes matter under GST

• They decide the GST rate. The code maps a product to its tax rate, so getting it right means charging the correct GST.
• They keep returns consistent. GSTR-1 summarises your sales by HSN code, so the codes on your invoices must match what you report.
• They are mandatory. HSN codes are required on GST tax invoices and in Table 12 of GSTR-1.

How many HSN digits does your business need?

The number of digits you must use depends on your aggregate annual turnover (AATO) in the previous financial year:

• Aggregate turnover up to ₹5 crore — 4-digit HSN codes. Mandatory on B2B invoices, optional for B2C.
• Aggregate turnover above ₹5 crore — 6-digit HSN codes, on all invoices.

A key point: the turnover that counts is the previous financial year's. If you crossed ₹5 crore in FY 2025-26, you must use 6-digit codes throughout FY 2026-27 — even if your turnover later dips below ₹5 crore.

Since the GSTN's Phase 3 update (return periods from May 2025), HSN codes in Table 12 of GSTR-1 must be picked from a dropdown rather than typed in freely. Manual, mismatched codes no longer slip through — another reason to get them right at the invoice stage.

How an HSN code is structured

Take an 8-digit Indian HSN code. Reading left to right, it narrows from broad to specific:

• The first 2 digits identify the chapter.
• The next 2 digits identify the heading.
• The next 2 digits identify the sub-heading (this is where the 6-digit international code ends).
• The last 2 digits are the India-specific tariff item.

A note on SAC codes

Goods use HSN codes; services use SAC codes — the Services Accounting Code. They work the same way. If you supply services, you will be quoting SAC codes instead.

Where you need HSN codes

• On every GST tax invoice you raise.
• In Table 12 of GSTR-1, where sales are summarised by HSN.
• In your item master, so the code is applied consistently every time.

Get it right once

The simplest way to stay compliant is to assign the correct HSN code to each item once — in your item master — and let your software carry it through to every invoice and return automatically.

That is exactly how Booksmor works: HSN and SAC lookup is built in, so you choose a code once and every invoice, e-invoice and GSTR-1 summary uses it correctly. Start a 30-day free trial and see your GST workflow simplified.