GST Calculator
Add GST to a base price, or pull it back out of a tax-inclusive amount — done the correct way, with the CGST/SGST or IGST split your invoice actually needs.
Work out the GST both directions
What filing GSTR-3B late costs late fee + 18% interest
Late fee is ₹50/day (₹25 CGST + ₹25 SGST), ₹20/day for a nil return — capped at ₹500 for nil, ₹2,000 / ₹5,000 / ₹10,000 by turnover otherwise. Interest under Section 50 is 18% p.a. on the cash liability for the days delayed. Indicative; the portal's computation is final.
§1The math — and the classic mistake
Adding GST is the easy direction. Extracting it from a tax-inclusive price is where invoices go wrong: you divide by (1 + rate), you do not knock the rate percent off the total.
The wrong version taxes the tax. On every reverse calculation — MRP to base price, rent inclusive of GST, a contractor's all-in quote — it's division, not subtraction.
§2The gotchas
The broad map: 5% covers essentials, goods transport and non-AC restaurants; 12% processed food and mid-range hotels; 18% most goods and nearly all services — the default assumption; 28% luxury and sin goods (cars, tobacco, aerated drinks). This is indicative — rates move at GST Council meetings, so confirm your item in the current rate schedule before invoicing.
“₹10,000” in a contract is ambiguous — is GST on top, or inside? On an 18% job that ambiguity is worth ₹1,800. Quotes, POs and MSME invoices should state “plus GST as applicable” or “inclusive of GST” in words. Silence usually gets read as inclusive — against you.
A composition-scheme dealer (turnover up to ₹1.5 crore) cannot charge GST on the invoice at all — the bill says “composition taxable person, not eligible to collect tax”. They instead pay 1–6% of turnover out of their own margin, and their buyers get no input credit.
Input tax credit means your business customer claims back the GST you charged — but only if the invoice is correct. Charge CGST+SGST on what was actually an inter-state supply (or vice versa) and their credit is blocked; they'll bounce the invoice back and your payment waits. The split isn't cosmetic.
§3Related
Pricing a business decision, not just an invoice? See what borrowing costs on the business loan EMI calculator, or price your working capital on the overdraft interest calculator.