To backwards calculate GST (find the original price before tax), divide the total GST-inclusive amount by 1 + ( GST Rate 100 ) 1 + ( G S T R a t e 1 0 0 ) . For a 10% rate, simply divide the total by 1.1. Then, subtract the original price from the total to find the GST amount.
Reverse GST Calculation Example
Subtracting GST:
To calculate how much GST is included in a price, just divide by 11. To calculate how much the price was before GST, just divide by 1.1.
Example
To calculate sales tax backwards from a total, divide the total price by (1 + the tax rate as a decimal) to get the pre-tax price, then subtract that pre-tax price from the total to find the actual tax amount. For example, for a $108 total with 8% tax, you'd calculate $108 / 1.08 = $100 (pre-tax), and then $108 - $100 = $8 (tax).
To determine the Reverse GST value, you need to calculate the amount of Base Price or the amount exclusive of GST. This can be done by using the formula given below. Once you have the base price, you can further calculate the Reverse GST amount by subtracting it from the GST-inclusive amount.
To calculate 20% backwards (find the original amount before a 20% decrease), divide the given final amount by 0.80 (which is 100% - 20%). For a 20% increase, divide the final amount by 1.20 (100% + 20%) to find the original. This method works by finding what percentage the final number represents (80% for a decrease, 120% for an increase) and then dividing to find the 100% base.
The formula for calculating GST is to multiply the net price (exclusive of GST) by 1.1 or divide the price including GST by 11 to determine the GST component.
Understanding GST Rate Reduction
Starting September 22, 2025, the GST Council reduced the number of tax slabs from four to two main rates: 5% merit rate for essential and priority items and 18% standard rate for most other goods and services. There is also a special 40% rate for luxury and sin goods.
How do you remove GST? The equation to subtract GST is slightly more complicated: First, take the GST-inclusive price and multiply that by 3. Then, divide the result by 23 and round that number to the nearest two decimal points.
Using Excel to Reverse Calculate GST
Here's how to do it: Use the Formula: To reverse calculate GST, the formula is =Total Price / (1 + GST rate). For example, if the total price is ₹118 with an 18% GST, the person would type =118 / 1.18' in Excel to find the original price of ₹100.
The value of a taxable supply is the consideration payable for the supply (before GST is added). For example, if the value of the supply is $100, the GST payable is 10 percent of $100, being $10. The price GST inclusive of the supply is $110. To work out the GST paid, you can divide by 11.
The reversal is calculated using the following formula. Example: If the buyer claimed ₹50,000 as ITC on a purchase, and the supplier failed to pay GST for 2 months out of 12 months, the ITC reversal would be calculated proportionately. As a result, the buyer must reverse ₹8,333 of the claimed ITC.
GST is a broad-based tax of 10% on most goods, services and other items sold or consumed in Australia. To work out the cost of an item including GST, multiply the amount exclusive of GST by 1.1. To work out the GST component, divide the GST inclusive cost by 11.
Any amount payable under reverse charge shall be paid by debiting the electronic cash ledger. In other words, reverse charge liability cannot be discharged by using input tax credit. However, after discharging reverse charge liability, credit of the same can be taken by the recipient, if he is otherwise eligible.
Net price = Original cost – GST
For example, if the cost of a product after GST of 18% is Rs. 118, its original cost is 118 – [100/(100 + 18%)}], which equates to Rs. 100.
Barring of GST Return on expiry of three years
The GST network issued another advisory on 7th June 2025, implementing the rule of time-barring of GST return filing beyond three years from the due date. By this update, taxpayers will not be able to file GST returns after three years from the due date of such return.
Types of GST in India
CGST (Central Goods and Services Tax) SGST (State Goods and Services. IGST (Integrated Goods and Services Tax) UTGST (Union Territory Goods and Services Tax)
Reverse Charge Mechanism & Calculation
To calculate the amount of GST/HST to remit, multiply the revenue from your supplies (including the GST/HST) for the reporting period by the quick method remittance rate, or rates, that apply to your situation.
Example:
To remove Value Added Tax or to make a reverse VAT calculation the formula is the following: Net: (Amount / 120) * 100 Easy! Divide the amount by 100 + VAT% and then multiply by 100. That's the amount excluding VAT taxes (Net amount).
Calculating reverse percentages