What this calculator does
This is the forward calculation: you know your taxable value — the price of the goods or services before tax — and you need the amount to put on the invoice. It also does the part people get wrong more often, which is splitting the tax correctly between the centre and the state.
The formula
Invoice total = Taxable value + GST amount
CGST = SGST = GST amount ÷ 2 (same-state supply)
IGST = GST amount (other-state supply)
Worked example
A studio bills ₹40,000 for a website build to a client in the same state. Marketing and IT services sit at 18%.
18% GST on ₹40,000
- Taxable value
- ₹40,000.00
- GST at 18%
- ₹7,200.00
- CGST at 9%
- ₹3,600.00
- SGST at 9%
- ₹3,600.00
- Invoice total
- ₹47,200.00
Had the client been in another state, the invoice would carry a single IGST line of ₹7,200 instead of the two ₹3,600 lines.
Which slab applies
| Slab | CGST | SGST | Typical supplies |
|---|---|---|---|
| 5% | 2.5% | 2.5% | Essential goods, economy transport, small restaurants |
| 12% | 6% | 6% | Processed food, business-class air travel, some apparel |
| 18% | 9% | 9% | Most services — marketing, software, consulting, IT |
| 28% | 14% | 14% | Luxury goods, automobiles, aerated drinks |
Most services sold by agencies, freelancers, software companies and consultants fall at 18%. If you are unsure about a specific supply, check the HSN or SAC code for your category rather than assuming — rates differ within categories more often than people expect.
What a compliant tax invoice needs
- Your GSTIN and the recipient's GSTIN where registered
- A serially numbered invoice number and date
- HSN or SAC code for each line
- Taxable value, rate, and tax amount shown separately for CGST, SGST or IGST
- Place of supply, especially for inter-state transactions
- Total invoice value in figures, and in words for higher values
The tax components must appear as their own lines. A single combined "GST" figure on an invoice is a common cause of ITC disputes for the buyer.
Frequently asked questions
What is the GST rate for digital marketing services?
Digital marketing, advertising and most IT-enabled services are taxed at 18% under GST, split as 9% CGST and 9% SGST for same-state supply.
When do I charge IGST instead of CGST and SGST?
When the place of supply is a different state from your registered location. The full rate goes on a single IGST line rather than being split.
Do I need GST registration to charge GST?
Yes. Collecting GST without a valid GSTIN is not permitted. Registration is generally required above ₹40 lakh turnover for goods and ₹20 lakh for services, with lower thresholds in special category states.
Is GST charged on the discounted price or the list price?
On the value after discount, as long as the discount is shown on the invoice itself and was agreed before or at the time of supply.