Every invoice you raise depends on getting one small detail right: the correct GST rate for the goods or service you are supplying, which in turn depends on the correct HSN or SAC code. Get the classification wrong, and you either overcharge customers, undercharge and create a liability gap, or run into GSTR-1 validation issues when your HSN summary doesn't line up with your declared rates.
This guide explains how the GST rate structure is organised, how HSN/SAC classification drives the rate you charge, and how to look up the correct rate before you invoice.
How the GST rate structure works
GST rates in India are organised around a small number of slabs, ranging from a nil or exempt rate for essential items to progressively higher slabs for standard goods and services, with an additional compensation cess layered on top of certain luxury or high-end category goods. The GST Council reviews and revises rates and slab structures periodically, including reclassifying specific items between slabs, so the exact slab an item falls into today may not be the one it fell into a year ago. Because of this, do not rely on a rate you memorised previously - always verify the current rate for your specific HSN/SAC on the official GST portal or the CBIC rate finder before invoicing.
HSN and SAC codes are the backbone of rate classification
The Harmonised System of Nomenclature (HSN) code classifies goods, while the Services Accounting Code (SAC) classifies services. Every rate notification is tied to an HSN or SAC (or a range of them), which is why classification - not the product description on your website - is what actually determines the rate you must charge. The number of digits you are required to declare on invoices and in returns generally depends on your turnover; see our guide on HSN code rules by turnover for the specifics.
How to find the correct GST rate for your product or service
- Identify the correct HSN (for goods) or SAC (for services) classification for what you are actually supplying - not a close substitute.
- Look up the rate against that HSN/SAC using the official GST rate finder on the GST portal, or the latest CBIC rate notification.
- Check whether a compensation cess applies in addition to the GST rate, which is common for select categories.
- Check for any specific exemption notification that might apply to your item or your buyer.
- When the classification is genuinely ambiguous - which happens more often than you'd expect with composite or mixed products - consult a tax professional rather than guessing.
Illustrative rate categories
The table below illustrates how categories are conceptually organised. It is not a rate card - treat every entry as an example of the type of classification, and confirm the exact current rate for your specific HSN/SAC before use.
| Example category | Typical treatment |
|---|---|
| Essential, unbranded food staples | Often nil-rated or exempt |
| Everyday consumer goods and common services | Lower standard slab |
| Most manufactured goods and general services | Standard slab |
| Luxury goods, select high-duty category items | Highest slab, often with compensation cess |
GST on services vs goods
Services are classified by SAC rather than HSN, and while the same slab logic applies, the correct rate also depends on getting the nature of the service right - a consulting service, a works contract, and a restaurant service can sit in different rate categories even though they might all loosely be described as services in casual conversation. Rate determination also interacts with where the supply is deemed to happen; see our guide on place of supply rules under GST for how that affects whether you charge CGST+SGST or IGST once you've settled on the rate.
Where rate classification shows up in your returns
Your GSTR-1 filing includes an HSN summary that aggregates outward supplies by HSN/SAC and rate. If your invoices use inconsistent HSN codes for the same product, or the rate applied on the invoice doesn't match what the code implies, this summary can throw validation warnings. Tools like GSTR-1 automation can flag these mismatches before you file, which is far less painful than discovering them after a notice.
Common rate-related errors sellers make
- Applying a rate based on a product category in general instead of the specific HSN it actually falls under
- Reusing an old HSN/SAC after a reclassification notification has changed its rate
- Forgetting to apply compensation cess where it is due
- Mixing exempt and taxable items on one invoice without splitting the tax correctly per line
- Not updating item masters or catalogue data after a rate change, so old invoices and new invoices disagree
Keeping rate data accurate as you scale
As your product catalogue grows - especially if you sell across multiple marketplaces with slightly different category structures - maintaining one clean, correct HSN-to-rate mapping becomes more valuable than looking up each item individually. This is part of what a structured inventory software item master is designed to help with as OneBooks GST's roadmap develops, alongside the GST calculator you can use today to sanity-check a rate.
Nil-rated, exempt, and zero-rated are not the same thing
These three terms get used interchangeably in casual conversation, but they mean different things for compliance purposes. A nil-rated supply is taxed at a 0% rate under the GST rate schedule itself. An exempt supply is one that is specifically kept outside the scope of GST by a notification, even though it might otherwise be taxable. A zero-rated supply - typically exports and supplies to SEZs - is taxable in principle but the tax is effectively neutralised, usually with the supplier still eligible to claim input tax credit on inputs, which is not automatically true for nil-rated or exempt supplies. Mixing these categories up on your GSTR-1 HSN summary or in your ITC computation is a common source of avoidable errors, so it's worth confirming which bucket a specific supply falls into rather than treating all three as no tax charged and stopping there.
Rate changes and your existing inventory
When a rate notification changes the slab for an HSN you deal in, the transition date matters as much as the new rate itself - invoices raised before the effective date generally follow the old rate, and those raised on or after typically follow the new one, though transitional provisions can apply to specific situations like advance receipts or ongoing contracts. If you carry inventory across a rate change, review your pricing and any old purchase orders that span the transition date so your invoicing stays consistent with the correct rate on the correct date.
Frequently asked questions
How many GST rate slabs are there?
GST is organised into a small number of slabs plus a nil/exempt category, with compensation cess applying on top for select goods. The exact number and composition of slabs is set by the GST Council and can change, so verify the current structure on the GST portal.
How do I find the GST rate for my product?
Identify the correct HSN or SAC code for what you are supplying, then look it up using the official GST rate finder on the GST portal or the latest CBIC notification.
What is the difference between HSN and SAC?
HSN codes classify goods, while SAC codes classify services. Both drive which rate slab and notification apply to a given supply.
Do GST rates change often?
Rates and slab structures are reviewed and revised periodically by the GST Council. Do not assume a rate you used previously is still correct - check before every significant filing cycle or catalogue update.
What happens if I use the wrong HSN code?
Using the wrong HSN can lead to charging the wrong rate, mismatches in your GSTR-1 HSN summary, and potential queries from the department. It's worth correcting item-level classification as soon as you spot an error.
How OneBooks GST handles it
OneBooks GST is a GST and accounting platform for Indian businesses. It imports sales data, prepares GSTR-1, parses bank statements, and exports to Tally XML, Miracle, Profit NX, Excel and CSV.
Keeping the original source file, the reviewed working copy and the final export together is what makes the same check repeatable next period, and OneBooks GST stores them against the filing period.
