GST in India: CGST, SGST, IGST and Invoice Basics (2026)

GST on an Indian invoice is usually one of two shapes: intra-state (CGST + SGST, each half the slab) or inter-state (IGST at the full slab). The arithmetic is short. The legal facts — place of supply, HSN, exemption notifications — are not. FlashKit’s GST calculator does the arithmetic locally. It does not file GSTR-1, GSTR-3B, or decide your place of supply.

Inclusive vs exclusive

  • Exclusive: tax = taxable value × rate. Payable = taxable + tax.
  • Inclusive: taxable = total ÷ (1 + rate). Tax = total − taxable.

Quoting a tax-inclusive workshop fee as if it were exclusive is how small vendors under-collect. Run both modes in the calculator before you send the PDF.

Estimate GST on a line item

5 / 12 / 18 / 28% slabs, inclusive or exclusive, CGST/SGST or IGST. Not a CA substitute.

Open GST calculator

CGST + SGST vs IGST

Same state (intra-state supply): split the slab. 18% becomes 9% CGST + 9% SGST. Different states (inter-state): 18% IGST. Union-territory supplies use UTGST in place of SGST in the statute — if your place of supply is a UT, ask the person who files your returns; the calculator’s IGST/CGST toggle is a teaching split, not a jurisdictional opinion.

What the tool will not do

  • Pick your HSN/SAC or tell you if a notification exempts the line.
  • Compute input-tax credit eligibility or inverted-duty refunds.
  • Replace the official GST portal or a practice-management suite.

For a longer invoice walkthrough with a 90-second ritual, see How to calculate GST on an Indian invoice.

When GST sits next to EMI or SIP

A machine bought on a loan has an invoice GST line and an EMI. Estimate tax with the GST tool, then principal + rate with the EMI calculator. Do not add GST into EMI principal unless the lender financed that tax. Retirement SIPs are unrelated to invoice GST; do not mix them except as cash-flow planning with the SIP calculator.

Disclaimer (not financial advice)

FlashKit calculators run reducing-balance EMI and compound-SIP arithmetic in your browser. They are planning aids, not a bank sanction letter, a GSTN filing, SEBI-registered investment advice, or a substitute for a chartered accountant. Actual EMI depends on processing fees, insurance, prepayment clauses, and the lender’s day-count. Mutual-fund returns are not guaranteed. Confirm numbers with your lender or advisor before you sign.

Related tools