A GST compliant invoice is not hard to produce once you know the rules — but one missing field or a broken number series can turn an ordinary bill into a problem during a return or an audit. For a clinic the job has an extra twist: most of your work is exempt, only some of it is taxable, and the document has to show both cleanly. Here is exactly what a tax invoice must carry, how the numbering and the tax split work, the mistakes clinics make most, and how to stop making them.
Key Takeaways
- A GST compliant invoice must carry set fields — your GSTIN, a consecutive number, the date, patient details, the HSN/SAC code, the taxable value and the CGST/SGST split.
- Invoice numbers must run consecutively and uniquely through the financial year, up to 16 characters — no skips, no repeats, no mid-year reset.
- Issue a tax invoice for taxable supplies and a bill of supply for exempt-only supplies; a mixed sale to an unregistered patient can go on one invoice-cum-bill of supply (Rule 46A).
- Within your state you charge CGST plus SGST, each half the rate; IGST applies only to inter-state goods movement.
- The reliable fix for every numbering and rate error is software that assigns the next number and pulls each item's HSN and GST rate on its own.
When you issue a tax invoice — and when you do not
You raise a GST tax invoice whenever you make a taxable supply: a pharmacy retail sale, a cosmetic procedure, a device sale, or any non-exempt service. For purely exempt healthcare, a GST-registered clinic issues a bill of supply instead — fewer fields, because no tax is charged. Most clinics in Patna, Varanasi and Muzaffarpur handle both in the same day, so your system has to switch between them without you thinking about it. When a single walk-in buys both — an exempt consultation and a taxable medicine — Rule 46A lets you put it all on one invoice-cum-bill of supply rather than two separate documents.
What a compliant invoice must contain
The GST rules spell out what a tax invoice must show. Miss one and the invoice is technically defective, which is the last thing you want a tax officer to find. These are the essentials.
| Field | Why it matters |
|---|---|
| Clinic name, address and GSTIN | Identifies you as the registered supplier |
| Consecutive invoice number (up to 16 characters) | Must be unique and unbroken for the year |
| Date of issue | Fixes the tax period |
| Patient or customer name | The recipient of the supply |
| Recipient GSTIN, if a registered business | Needed for them to claim input credit |
| Description of the goods or service | What was actually supplied |
| HSN code (goods) or SAC code (service) | Classifies the item and its rate |
| Quantity and taxable value | The base the tax is worked out on |
| Tax rate and amount (CGST/SGST or IGST) | The GST actually charged |
| Place of supply, for inter-state sales | Decides CGST/SGST versus IGST |
| Total invoice value | What the patient pays |
| Signature or digital signature | Authenticates the document |
The numbering rule people break
Invoice numbers have to be consecutive, unique within the financial year, and no longer than 16 characters using letters, numbers, the hyphen and the slash. A prefix is fine — CLN/2026-27/0001 — but you cannot skip a number, reuse one, or reset the series in the middle of the year. Gaps and duplicates are the first thing scrutiny looks for. This is precisely where handwritten bill books fail: a page gets torn out, a number gets written twice, a carbon copy goes missing. Software that hands you the next number automatically removes the whole risk.
Keeping exempt and taxable lines straight
Because a clinic bill mixes exempt care with taxable goods, the layout matters. Show the exempt lines — consultation, treatment — clearly as exempt with nil tax. Show the taxable lines — medicines, a cosmetic procedure — with their taxable value, the rate, and the CGST/SGST amounts. Within your state the tax always splits in half: a 12% medicine is 6% CGST and 6% SGST. You only reach for IGST when the place of supply is another state, for example a device shipped out of Bihar to a buyer elsewhere. Getting the head right matters, because the wrong one lands in the wrong return. If you are still unsure which of your lines are taxable at all, start with what is exempt versus taxable in a clinic.
The mistakes clinics make most
- Skipping, repeating, or resetting invoice numbers in the middle of the year.
- Charging IGST on a local sale, or splitting into CGST/SGST on an inter-state one.
- Leaving off the HSN/SAC code or the clinic GSTIN.
- Putting tax on exempt consultation lines, or hiding taxable medicines inside an exempt total.
- Rounding tax inconsistently between the line items and the grand total.
- Raising a full tax invoice for an exempt-only visit instead of a bill of supply.
Where Clinizy Care fits
Clinizy Care turns all of this into a single button. Your clinic name, address and GSTIN are stored once and print on every bill. Invoice numbers are assigned automatically in an unbroken series, so a gap or a duplicate is simply not possible. Each catalogue item carries its own HSN or SAC code and GST rate, so the moment you add a line the software works out the taxable value and the correct CGST/SGST split, keeps exempt and taxable lines apart, and produces a clean, compliant invoice in seconds. You can send it to the patient over WhatsApp in Hindi or English, and the owner view keeps a running total of taxable collections for your returns.
This is part of Care Essentials at ₹1,999 a month, built for a solo doctor or small clinic. If you want the wider GST-ready billing software picture across pharmacy and departments, Care Plus covers it. The fastest way to judge it is to raise a real mixed bill yourself on the 30-day free trial — no credit card — and watch the numbering and the tax split handle themselves.