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HSN and SAC Codes: How to Find the Right One for Your Invoice

By Nikitha Thobias · 5 August 2026 · 10 min read

What HSN and SAC codes are, how many digits your invoice must show, how to find the correct code for your product or service, and the errors that break your GSTR-1 summary.

Why one small field on the invoice causes so much trouble

Every taxable line on a GST invoice needs a classification code: HSN for goods, SAC for services. It looks like a formality — a number in a narrow column that nobody reads. In practice that code is the thing the entire tax treatment hangs from. It determines the rate you are supposed to charge, it decides whether your customer's input tax credit survives scrutiny, and it is the key your GSTR-1 HSN summary is built on.

The typical situation in a small business is this: somebody set up the item list once, could not find the right code for half the items, and put in whatever looked close. Nothing goes wrong for months. Then a corporate customer's accounts team rejects an invoice, or the HSN summary in a return refuses to tie up with the sales figure, and suddenly the codes for two hundred items have to be revisited during filing week.

This article explains what these codes are, how many digits you actually have to print, how to find the right one without guessing, and the specific errors that create reconciliation problems later.

What HSN and SAC codes actually are

HSN stands for Harmonised System of Nomenclature — an internationally used system for classifying goods, adopted under GST so that the same product carries the same classification everywhere. SAC, the Services Accounting Code, does the same job for services.

How an HSN code is structured

HSN codes are hierarchical, and understanding the hierarchy is what lets you narrow down a code instead of hunting for an exact phrase:

• The first two digits are the chapter — the broad family the goods belong to.
• The next two make the heading — a narrower group inside that chapter.
• The next two are the subheading, and further digits give the specific tariff item.

So a code gets more specific as it gets longer, and a 4-digit code is a parent of the 6- and 8-digit codes beneath it. When you cannot find your exact product, the practical method is to identify the chapter first, then read down the headings until the description stops fitting.

How SAC codes work

Service codes sit under a services grouping, and are read the same way — a broad group narrowing to a specific service. Maintenance, repair and installation services, construction services and support services each occupy their own group, and a service business usually needs only a handful of codes in total, unlike a trader with a wide catalogue. The catch for service businesses is the opposite of the trader's problem: because there are so few codes to set up, nobody sets them up at all, and invoices go out with the column blank.

How many digits you must show

This is the part that has changed over time and where most outdated setups sit. The requirement is tied to your aggregate turnover: below a threshold you may show fewer digits, above it you must show more, and B2B supplies are treated more strictly than B2C. The direction of travel has been consistently towards more digits for more businesses.

Two practical consequences:

• Crossing a turnover band is a software task, not just an accounting one. If your turnover moved you into a higher requirement this year, the item master needs longer codes before your next invoice, not before your next audit.
• Do not assume your current setting is right because it was right once. Check the requirement for your present turnover band, then check that your item master actually carries codes of that length for every item — not just for the ones you sell most.

Finding the right code: a method that works

Guessing from a search result is how wrong codes enter a system. Use a sequence instead:

• Write the item description the way a tariff would. Not “AC service kit” but what the thing physically is — material, function, whether it is a part or a complete article. Half of code-hunting is describing the item properly.
• Use the GST portal's rate finder and the tariff. Start from the chapter, then narrow. These are the authoritative sources.
• Cross-check against a supplier invoice. If you buy the same item from an established distributor, the code on their invoice is a strong signal — they have usually had it reviewed.
• Sanity-check the code against the rate. The rate you believe applies and the rate associated with the code must be the same. If they are not, one of the two is wrong, and finding out which one now is far cheaper than after fifty invoices.
• Get ambiguous cases confirmed in writing. Composite items, kits, refurbished goods and anything where two headings could plausibly fit are worth a specific answer from your CA, kept on record.

The mixed invoice: parts plus labour

Service businesses that fit spare parts hit a case traders never do. A single invoice may carry a compressor (goods, HSN, one rate) and the installation labour (service, SAC, possibly a different rate). Those are two lines with two codes and potentially two rates on one document — not one line called “AC repair” at whatever rate seems reasonable.

Where the supply genuinely is a single bundled service with parts consumed in it, the treatment can differ. This is exactly the kind of case worth confirming once with your accountant and then encoding into your item master, so the technician closing the job does not have to make a tax decision on site. Our piece on inventory for service businesses that carry spare parts covers the stock side of the same problem.

Implementation steps: build a code master once

• Put the code on the item, not on the invoice. Every product and service in your catalogue gets its HSN or SAC code, its unit and its rate stored once. The invoice then picks them up. Codes typed per invoice will be inconsistent within a week.
• Do the whole catalogue in one pass. Sort items by sales value and work down. The long tail matters less commercially but a single wrong code there still breaks a summary.
• Record the source of each decision. A column noting “from tariff”, “from supplier invoice”, or “confirmed by CA on date” turns a future query into a two-minute answer.
• Reconcile the HSN summary before filing, not during. Your GSTR-1 HSN summary should tie to your sales register. Reviewing it monthly surfaces a wrong code after a few invoices instead of after a year. Our monthly GSTR-1 and GSTR-3B routine sets out where this check fits.
• Re-review after any rate change. When a rate moves, the affected items need checking — the code stays but the rate mapped against it in your system may not have been updated.
• Lock editing. Codes should be changeable by whoever owns the item master, not by everyone who raises an invoice.

Common mistakes

• One generic code for a mixed catalogue. Fast to set up, guaranteed to mismatch, and obvious in an HSN summary.
• Fewer digits than your turnover requires. A silent defect — the invoice looks fine and is still non-compliant.
• A code that contradicts the rate charged. The single most consequential error, because it puts your customer's credit at risk and makes you the supplier their accounts team flags.
• Using an HSN code on a service line (or a SAC on goods). Common on mixed invoices raised in a hurry.
• Changing a code mid-year without a reason on record. Your annual HSN summary then shows the same item under two codes, which looks like an error even when the new code is the correct one. Change it deliberately, note the date and why.
• Copying a code from a marketplace listing or a random blog. Plenty of these are stale. The tariff and the portal are the sources; everything else is a hint.
• Leaving the column blank on service invoices because the old invoice format never had it.
• Fixing an issued invoice by editing it. A wrong code on an issued invoice is corrected by a credit or debit note, not a silent edit — the same rule that applies to any other invoice error, as covered in GST invoicing for service businesses.

What to do about it

Treat the code as part of the item, decided once by someone who checked the tariff, and never as a field the person raising the invoice fills in from memory. That single change removes most classification errors, because it moves the decision from a hundred hurried moments to one considered one.

Software helps here only to the extent that it stores the code with the item, applies it automatically to every invoice, and gives you an HSN summary you can reconcile before filing. VeloCrew's GST invoicing keeps HSN and SAC codes on the item master and carries them into the invoice and the HSN summary, and its GST accounting side produces the summaries you check before a return. The code still has to be right — but it only has to be got right once.

General guidance only, not professional advice. Classification, rates and the digit requirements tied to turnover change — confirm the current requirements for your business with a qualified professional.

Frequently asked questions

What is the difference between an HSN code and a SAC code?

HSN codes classify goods and SAC codes classify services. Both are used the same way on a GST invoice and in returns, and both drive the applicable tax rate. If you sell a spare part you use an HSN code; if you bill the labour to install it, that line takes a SAC code.

How many digits of HSN do I need to show on my invoice?

The number of digits required depends on your aggregate turnover, with smaller businesses required to show fewer digits and larger ones more, and B2B supplies treated more strictly than B2C. Because the thresholds have been tightened over time, check the requirement that currently applies to your turnover band rather than relying on what your software was set up with two years ago.

Can I use one HSN code for everything I sell?

No. The code has to describe the actual goods or service on that line, because the code and the rate must agree. A single generic code across a mixed catalogue is one of the easiest mismatches for a system to spot, and it makes your HSN summary in GSTR-1 meaningless.

Where can I look up the correct code?

The GST portal's rate finder and the official tariff are the authoritative sources, and the code on a reputable supplier's invoice for the same item is a useful cross-check. Random results from a search engine or a marketplace listing are not — several sites publish outdated codes. For anything ambiguous or high value, confirm with your CA in writing.

What happens if I use the wrong HSN code?

The immediate consequence is a mismatch: the rate you charged may not match the code you declared, your customer's input tax credit can be questioned, and your GSTR-1 HSN summary will not reconcile with your sales. There can also be a penalty for an incorrectly issued invoice. Correcting the master and issuing a credit or debit note is cheaper than leaving it.

Do I need a SAC code if I only provide services?

Yes. Service invoices carry SAC codes on each taxable line, subject to the same digit requirements based on turnover. Service businesses often overlook this because their invoices historically had no code at all, then find their returns will not reconcile.