Find the base price when you only have the GST-inclusive total. Useful for reconciling purchase invoices, working back from MRP, and checking supplier quotations.
Reverse GST calculation — extracting the base price from a tax-inclusive amount — is what you need when working backwards from MRP, reconciling purchase invoices, or checking whether a supplier has priced inclusive or exclusive.
The formula is base = inclusive ÷ (1 + rate). The frequent error is subtracting the rate from the inclusive amount instead, which overstates the tax portion and understates your true cost.
MRP ₹590 at 18% GST: base = 590 ÷ 1.18 = ₹500, GST = ₹90. Subtracting 18% of 590 (₹106.20) would be wrong by ₹16.20 per unit — multiplied across a carton, real money.
Because the 18% was charged on the base, not on the final amount. Subtracting from the inclusive amount applies the rate to a bigger number and inflates the tax you think you paid.
MRP-based pricing decisions, claiming correct ITC from inclusive purchase bills, rate-contract negotiations quoted 'landed', and audit reconciliations of inclusive receipts.
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