How HSN is structured
The Harmonized System is hierarchical, and each level narrows the classification.
- First two digits — chapter, the broad category
- Next two — heading within that chapter
- Next two — subheading, the six-digit international code
- Final two — national tariff item, specific to India
Getting classification right
Classification follows the General Rules of Interpretation: the most specific description wins over the general, composite goods are classified by the component giving them their essential character, and where nothing else settles it, the heading occurring last in numerical order applies. Where genuinely unclear, an advance ruling gives binding certainty.
Why it belongs on the item, not the invoice
Because the code drives the rate, storing it against the item master means every invoice line inherits both. Typing it per invoice invites drift — the same product classified two ways across two months is exactly the pattern that surfaces during reconciliation.
Reporting in GSTR-1
The HSN summary table in GSTR-1 aggregates your outward supplies by code, quantity and value. It only reconciles cleanly if the codes on the underlying invoices were consistent, which again points back to the item master.
Common questions
What happens if I use the wrong HSN code?+
If it leads to a lower rate being charged, you are liable for the shortfall plus interest, and a penalty may apply. If it leads to a higher rate, your customer has overpaid and will want a credit note. Either way the correction runs through your returns.
Do services need HSN codes too?+
Services use SAC codes, which sit inside the same classification system and all begin with 99. Functionally they serve the same purpose.
Is HSN mandatory on B2C invoices?+
The reporting requirement is lighter for B2C, but since the code determines the rate you are applying anyway, there is little practical reason to omit it.