Reverse GST Calculator

Work backwards from a GST-inclusive total to find the original GST-exclusive amount. Perfect for auditing, verification, and reverse calculation needs for Australia businesses.

Select Country

Calculation Mode

Add GST

Calculate total with GST added

Remove GST

Extract GST from total price

Reverse GST

Find pre-tax amount

GST Only

Calculate GST amount only

Enter Amount (AU$)

AU$

Australia GST Rate: 10% (current rate for 2026)

Quick examples:

How Reverse GST Calculation Works

Reverse GST calculation determines the original base amount:

Enter the final GST-inclusive total
Select your country (Australia)
Get the original amount before GST was added

Formula: Original Amount = Total ÷ (1 + 0.1) = Total ÷ 1.1

Reverse Calculation Examples

Final Total (with GST)	GST Component (10%)	Original Amount
AU$110.00	AU$10.00	AU$100.00
AU$550.00	AU$50.00	AU$500.00
AU$1100.00	AU$100.00	AU$1000.00

When to Use Reverse GST Calculation

Audit Verification: When checking if GST was calculated correctly on invoices
Pricing Analysis: When determining original costs from retail prices
Error Correction: When fixing incorrectly calculated GST amounts
Reconciliation: When matching records between GST-inclusive and exclusive systems
Historical Analysis: When analyzing past transactions to determine base amounts

Reverse vs Remove GST

Reverse GST and Remove GST use the same calculation method but differ in context. Use "Reverse" when auditing or verifying calculations, and "Remove" when processing receipts or accounting records.

Related Calculators

Add GST Calculator

Add GST to base amounts for invoicing and pricing

Remove GST Calculator

Calculate the GST-exclusive amount from totals

Australia GST Calculator

Full-featured calculator for Australian 10% GST

New Zealand GST Calculator

Full-featured calculator for New Zealand 15% GST

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