GST for watch repair shops, minus the confusion

Almost nobody who runs a watch repair counter set out to become a part-time tax clerk, and yet GST ends up being the part of the job with the least room for a shrug. Get the rate wrong and it’s a small loss on one invoice. Get the split wrong across a year of invoices, and it’s a pattern your filing has to answer for. None of this is complicated once it’s laid out properly, so here’s the version we wish someone had explained to us plainly the first time.

Where the tax actually gets charged: place of supply

The instinct is to think GST depends on where your shop is. It doesn’t, not directly. GST is charged based on the customer’s location, what the law calls the place of supply. Your shop being registered in one state doesn’t mean every invoice you write uses that state’s numbers; it means that state is one half of a comparison you make on every single invoice, the other half being wherever your customer is.

Same state or different state: the split that actually matters

Once you know both sides of that comparison, the rule is genuinely simple:

• If your shop’s state and the customer’s place of supply are the same, the tax splits evenly in half: CGST (central) and SGST (state), each at half the total rate.
• If they’re different, there’s no split. The full rate is charged as a single line, IGST, and nothing is divided.

Here’s the part that trips people up: the customer pays the same total either way. A repair billed at Rs 1,000 plus 18% tax is Rs 1,180 whether it’s split 9% CGST plus 9% SGST for a local customer, or charged as a flat 18% IGST for someone in another state. The split doesn’t change what anyone owes. It changes how the government’s books record who gets which slice of it, central government or state government, which is exactly why getting it right (or wrong) shows up in your GSTR-1 filing rather than in your customer’s wallet.

If you genuinely don’t know a customer’s state, because they walked in, paid cash, and you never asked, the practical fallback is to treat them as being in your own state until you have a reason to think otherwise. It won’t always be technically perfect, but it’s a defensible default, and it’s far better than leaving the field blank.

HSN and SAC: two different worlds, and repair lives in the second one

Every line on a GST invoice needs a classification code, and watches sit in a slightly confusing spot because a shop deals with both goods and services on the same invoice. A watch, a strap, a part you sell outright, is a good, and goods in the watch category generally fall under heading 9102 (wristwatches, as distinct from 9101’s precious-metal-cased watches). But repair work itself isn’t a good changing hands, it’s labour and expertise, and that puts it under the 9987 family of SAC codes: maintenance and repair services. The distinction matters because using a goods code for a service line (or vice versa) is exactly the kind of mismatch a departmental review flags first, even when the tax amount itself happens to be correct.

Practically: if a line item is “battery replacement, part cost,” that’s arguably a goods component. If the line is “labour, movement service,” that’s squarely a 9987-family service. Plenty of real invoices have both kinds of lines, and that’s fine, as long as each line carries the code that actually matches what it’s billing for.

Numbering discipline, the boring rule that saves you

GST expects a clean, sequential invoice series, one running number per financial year, with no gaps and nothing reused, not even for an invoice you cancelled five minutes after issuing it. It’s tempting to renumber around a mistake so the sequence “looks right.” Don’t. A sequence with an honest gap in it (invoice 41 was voided, here’s why) reads as ordinary bookkeeping. A sequence with numbers quietly reused or reordered reads as something to look into.

This is not tax advice

Everything above describes the mechanics as they generally apply to a small repair shop’s invoices. It is not a substitute for actual advice on your specific numbers: registration thresholds, whether the composition scheme could apply to you, reverse charge situations, e-invoicing requirements once you cross certain turnover levels, all of that depends on details a page like this can’t see. The first time you’re unsure, or the first time you cross a threshold you haven’t dealt with before, an hour with a CA is worth more than an afternoon of forum threads.

We built invoicing that handles the CGST/SGST/IGST split automatically off the customer’s state, since it’s exactly the kind of arithmetic a computer should be doing instead of a person at a busy counter. If that’s useful to you, it lives at /bench. If not, the rules above are yours to use by hand regardless.