Every item in your inventory needs an HSN code (for goods) or SAC code (for services) — not just for the GST rate it determines, but because that code becomes the basis for the HSN-wise summary in your GSTR-1 and the classification your buyers see on their invoices. Getting HSN/SAC codes for inventory wrong does not just risk an incorrect GST rate; it can create mismatches that are tedious to unwind months later.
This guide explains what HSN and SAC actually are, how many digits you need at your turnover level, how to map codes onto your item master, and the mistakes that show up most often in inventory records.
HSN and SAC: What They Are
HSN (Harmonised System of Nomenclature) is an internationally standardised numeric coding system for classifying goods, originally developed for customs and trade, and adopted under GST to classify products for tax rate purposes. SAC (Services Accounting Code) is the equivalent system for services, maintained separately under GST. If your inventory is physical goods, you will be working almost entirely with HSN; SAC becomes relevant if you also invoice for services like installation, AMC or freight alongside goods.
HSN vs SAC at a Glance
| HSN | SAC | |
|---|---|---|
| Applies to | Goods | Services |
| Digit structure | Up to 8 digits, hierarchical (chapter, heading, sub-heading, tariff item) | 6 digits, all beginning with 99 |
| Origin | International customs classification | India-specific, adapted for GST |
| Where you will use it | Item master, purchase/sale invoices, GSTR-1 HSN summary | Service invoices, GSTR-1 where services are billed |
| Example | 6109 (T-shirts, knitted) | 998719 (maintenance and repair services) |
How Many HSN Digits Your Invoices Need
The number of HSN digits required on a tax invoice is tied to annual turnover, and this threshold has changed across past GST notifications, so treat the figures below as a general guide and confirm the current requirement on the official GST portal (www.gst.gov.in) or with your GST practitioner before relying on it.
| Annual Turnover (previous FY) | HSN Digits Typically Required | Applies To |
|---|---|---|
| Up to around ₹5 crore | 4 digits | Mandatory on B2B tax invoices; optional but recommended on B2C |
| Above around ₹5 crore | 6 digits | Mandatory on all tax invoices (B2B and B2C) |
| Certain notified categories | 8 digits | Regardless of turnover, for specifically notified goods |
Whatever the exact current threshold, the practical rule is the same: it is safer to record more digits than the minimum required in your item master, since you can always truncate on the invoice, but you cannot add precision you never captured.
Reading the Structure of an HSN Code
An HSN code is hierarchical — each pair of digits narrows the classification further. Take 61091000 as an example:
- 61 — Chapter: articles of apparel and clothing accessories, knitted or crocheted.
- 6109 — Heading: T-shirts, singlets and other vests, knitted or crocheted.
- 610910 — Sub-heading: of cotton.
- 61091000 — Tariff item: further specification at the 8-digit level.
For most GST invoicing purposes you will stop at 4, 6 or 8 digits depending on your turnover slab, but understanding the hierarchy helps when you are deciding between two similar-looking codes for a new product.
Mapping HSN/SAC Codes to Your Item Master
The most common source of HSN errors is not picking the wrong chapter — it is inconsistency at the item level. A few practices help:
- Assign the HSN code once, at the SKU level, in your item master, not per invoice or per sale. Every invoice line for that SKU should then inherit the same code automatically.
- Where a single product has variants (size, colour), the HSN code is usually the same across variants unless the material composition genuinely changes it. Do not let colour or size create unnecessary HSN variation.
- Review the HSN assignment whenever a product's material or composition changes, for example switching a garment from cotton to a cotton-polyester blend, since that can shift the correct chapter or sub-heading.
- Keep a short justification note against unusual or borderline HSN choices — it saves time if a buyer, auditor, or you six months later needs to understand why a code was chosen.
How HSN Feeds the GSTR-1 HSN Summary
Your GSTR-1 return includes an HSN-wise summary table that aggregates outward supplies by HSN code, quantity, value and tax rate. If your item master has inconsistent or incorrect HSN codes, this summary can show mismatched tax rates against the same effective product, or split a single product's sales across multiple codes for no real reason — both of which tend to draw questions during a departmental review. Keeping HSN assignment clean at the inventory level, rather than fixing it invoice-by-invoice at filing time, is the more reliable approach.
Common HSN Mistakes to Avoid
- Using a generic or "closest guess" HSN code instead of checking the actual classification, especially for new product categories.
- Applying different HSN codes to what is effectively the same product across different sales channels or marketplaces.
- Not updating HSN records when GST rate notifications change the rate attached to a code.
- Recording fewer digits than your turnover slab requires, then discovering the gap only at filing time.
- Treating a service component, such as installation, warranty or freight billed separately, with a goods HSN code instead of the correct SAC.
How to Find the Right HSN Code for a Product
Start with the official HSN search tool on the GST portal or the CBIC customs tariff, which lets you search by product description or drill through the chapter structure. Cross-check against how similar sellers in your category classify the same product, and when a product genuinely straddles two classifications, document your reasoning rather than picking arbitrarily. For high-value or ambiguous cases, a quick check with your GST practitioner is worth the time compared with correcting HSN summaries after the fact.
Where OneBooks GST Is Headed
An item master with HSN/SAC mapped per SKU, feeding directly into the GSTR-1 automation HSN summary, is part of the inventory capability planned for OneBooks GST, described in more detail on the inventory software page and in our roadmap guide on supported stock workflows. For invoice-level rules around HSN digits, see our guide on HSN codes on invoices by turnover, and for rate lookups, GST rates in India by HSN.
Frequently asked questions
Do I need a different HSN code for each product variant?
Usually no. Colour and size variants of the same underlying product typically share one HSN code, unless the material composition genuinely differs between variants, for example a cotton version versus a polyester-blend version of the same garment style.
What happens if I use the wrong HSN code on an invoice?
It can result in an incorrect GST rate being applied, mismatches in your GSTR-1 HSN summary, and complications for your buyer's input tax credit if the rate charged does not match the correct classification. If you spot an error, correct it going forward and consult your GST practitioner on how to handle already-filed periods.
Is SAC ever relevant if I only sell physical products?
It can be, if you also invoice for services alongside the goods, such as installation charges, annual maintenance contracts, or separately billed freight. Those service line items need their own SAC code rather than being folded into the goods' HSN code.
How many HSN digits should I capture in my item master, even if fewer are required on invoices?
Capture the maximum precision you reasonably can, typically 6 or 8 digits, even if your current turnover only requires 4 digits on invoices. It is easier to show fewer digits on an invoice than to retroactively add precision you never recorded.
Where can I officially verify the current HSN digit requirement for my turnover?
Check the current notification on the official GST portal at www.gst.gov.in, since the turnover thresholds and digit requirements have been revised in the past and may change again.
Where software takes over: OneBooks GST
Once the source files are in hand, OneBooks GST covers the sales and GST side today, with SKU, HSN/SAC, valuation and warehouse-wise stock planned rather than shipped.
OneBooks GST keeps source data, reviewed output and exports as separate records, so a figure can be traced back rather than reconstructed.
