How do I back-calculate GST from an inclusive amount?
Tax amount = Inclusive × GST rate / (100 + GST rate). Base price = Inclusive - Tax. Example: a ₹1,180 invoice at 18% contains ₹1,000 base + ₹180 tax. Calculator handles this automatically.
GST & Business
Reverse GST Calculator
Quick answer: The FinTax24 Reverse GST Calculator extracts the base price and tax amount from any GST-inclusive invoice across all five slabs (5% / 12% / 18% / 28%) for both intra-State (CGST + SGST) and inter-State (IGST) supplies. It is the standard tool for retail reconciliation, MRP back-calculation and expense-claim reclassification.
Calculate reverse charge GST on inward supplies.
How to use this calculator
Follow these 4 steps for an accurate result.
- 1
Enter the inclusive amount
Type the value shown on the GST bill — typically MRP or total invoice value including tax.
- 2
Choose the GST rate
Pick 5%, 12%, 18% or 28% (or 0% for exempt categories) based on HSN/SAC classification.
- 3
Pick intra vs inter-State
Intra-State splits into CGST + SGST, inter-State uses IGST only.
- 4
Read base + tax breakdown
See base price, total tax, and CGST / SGST or IGST components instantly.
Key takeaways
- Single-formula reverse-GST math: Inclusive × Rate / (100 + Rate) = Tax component.
- Splits the tax into CGST + SGST (intra) or IGST (inter) based on transaction type.
- Helps reconcile reverse-charge invoices, inter-State purchases, and TDS-claim computation.
- Works for MRP back-calculation, expense-claim filings and composition-scheme tax adjustments.
Frequently asked questions
Quick answers to common questions about reverse gst calculator.
Is reverse GST required for reverse-charge invoices?
Yes — for reverse-charge purchases (advocate fees, renting from unregistered landlord, GTA service, etc.), reverse-GST math determines the GST component that you must self-pay to the Government. The supplier does not collect it — you compute it on their behalf.
Does reverse GST apply on MRP-based billing?
Yes, retail customers and dealers often need to back-calculate the GST component included in MRP for GST-claim, ITC reconciliation or audit trails. Use this calculator on the printed MRP to extract the embedded tax.
What if the GST rate is 0%?
Reverse-GST on a 0% rate produces zero tax and the base price equals the invoice amount. Useful for exempted goods (fresh produce, education, healthcare) where no GST is embedded but downstream ITC-claim corrections need explicit confirmation.
How does composition scheme adjust reverse GST?
Composition taxpayers cannot claim ITC, but they often receive inclusive bills. Reverse-GST math still works — the buyer can confirm the embedded tax, but the seller (composition dealer) is exempt from collecting it. Hence the actual tax outflow may be lower for composition businesses.
Can I reverse-calculate IGST for inter-State purchase?
Yes. Choose Inter-State mode and the calculator shows the entire GST as IGST. For IGST adjustment against output liability, the GST portal auto-populates GSTR-2B with line-wise tax components, which the calculator numbers reconcile against.
Key sources: CBIC GST portal, CGST Act Section 9 (rate schedule), E-way Bill system.
Reviewed by FinTax24 Content Team · Review date
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