FAQ
Frequently Asked Questions
How do I extract GST from a GST-inclusive total? +
Formula: Base Price = Total ÷ (1 + GST Rate ÷ 100). Then GST Amount = Total − Base Price. For CGST + SGST split: each = GST Amount ÷ 2.
Example: Total = ₹1,180, GST Rate = 18%
Base = 1180 ÷ 1.18 = ₹1,000
Total Tax = ₹180 → CGST = ₹90, SGST = ₹90
What is the reverse GST (tax reverse) formula? +
There are two equivalent formulas:
Base Price = Total × 100 ÷ (100 + GST Rate)
GST Amount = Total × GST Rate ÷ (100 + GST Rate)
For 18% GST that becomes Total × 18 ÷ 118. For 5% GST it is Total × 5 ÷ 105. The calculator above applies these formulas for you and splits the tax into CGST + SGST (intra-state) or IGST (inter-state).
How do I calculate 18% GST in reverse? +
Divide the GST-inclusive total by 1.18 to get the base price.
Example: Total = ₹2,360
Base = 2360 ÷ 1.18 = ₹2,000
GST = ₹360 → CGST = ₹180, SGST = ₹180 (or IGST = ₹360 for an inter-state sale)
How do I reverse-calculate 5% GST on a restaurant bill? +
Most standalone restaurants in India charge 5% GST. To find the food value from the final bill, divide by 1.05.
Example: Bill total = ₹525
Food value = 525 ÷ 1.05 = ₹500
GST = ₹25 → CGST = ₹12.50, SGST = ₹12.50
Touch4Bill's restaurant billing software prints this split on every bill automatically.
How do I remove GST from an MRP price? +
MRP in India is GST-inclusive. Enter the MRP as the total, select the product's GST rate, and the calculator shows the pre-tax price. Manually: MRP ÷ (1 + GST Rate ÷ 100). For an item with MRP ₹590 at 18% GST, the base price is 590 ÷ 1.18 = ₹500 and the GST is ₹90.
What is the difference between reverse tax and reverse charge mechanism (RCM)? +
Reverse Tax Calculation (this tool) means mathematically extracting the base price and tax from a tax-inclusive total. It's a calculation, not a legal concept.
Reverse Charge Mechanism (RCM) is a GST legal provision where the recipient of goods/services is liable to pay GST instead of the supplier. Examples: Goods Transport Agency (GTA) services, advocate services, import of services. These are separate concepts.
Can I claim input tax credit (ITC) on GST I calculate here? +
You can claim ITC on GST paid on your
business purchases, provided:
- The supplier has filed their GSTR-1 and the entry appears in your GSTR-2B
- You have a valid tax invoice from the supplier
- The goods/services are used for business purposes
- You are GST registered
Note: Restaurants under the 5% GST scheme are NOT eligible to claim ITC on inputs.
Why does my calculator show different results from my accountant's figure? +
Common reasons: (1) The GST rate used may differ — make sure you're using the correct rate for the specific goods or services. (2) Some invoices may have mixed rates (some items at 5%, others at 12%). Use the Multi-Item mode to handle mixed-rate bills. (3) Rounding differences — GST invoices round to the nearest paisa, which may cause minor differences.
How does billing software handle reverse GST automatically? +
Good billing software like Touch4Bill stores the HSN code and GST rate for every product. When a purchase or sale is recorded, it automatically calculates the base price, CGST, and SGST — no manual reverse calculation needed. It also reconciles ITC claims by matching purchase GST with GSTR-2B data.
Learn about Touch4Bill's GST billing →