Remove GST (Reverse GST) Formula Explained, With Examples
Every remove gst (reverse gst) result comes from one formula. Once you understand what goes into it, you can sanity-check any figure you are given, whether by an employer, a bank, a teacher or another website.
The formula
GST portion = inclusive price × 9/109.
What each input means
- Price including GST (S$): the value you enter in the calculator.
Example
For example, with these inputs:
- Price including GST (S$): 109
the calculator returns:
- GST included: S$9.00
- Price before GST: S$100.00
How the result changes
The table keeps the other inputs at their example values and changes price including gst (s$).
| Price including GST (S$) | GST included | Price before GST |
|---|---|---|
| 109 | S$9.00 | S$100.00 |
| 54.5 | S$4.50 | S$50.00 |
| 81.75 | S$6.75 | S$75.00 |
| 136 | S$11.23 | S$124.77 |
| 164 | S$13.54 | S$150.46 |
Why it matters
Singapore's tax system is simple by global standards, but the progressive bands, reliefs and the 9% GST still trip people up. A quick calculation helps you set aside the right amount before IRAS sends your notice of assessment, or check that a bill has been worked out correctly.
Reliefs lower chargeable income before rates apply. Common ones include earned income relief, CPF relief for employee contributions, parent and handicapped parent relief, working mother's child relief, NSman relief, course fees relief, and relief for SRS contributions and CPF cash top-ups. Total personal reliefs are capped at S$80,000 a year.
IRAS issues a notice of assessment, usually from April onwards, and tax is due within a month, although most people opt for interest-free GIRO instalments. Estimating your bill early means you can budget for it instead of being surprised.
Tax planning in Singapore is mostly about timing and reliefs rather than complex structures. Topping up CPF, contributing to SRS and claiming every relief you qualify for can lower your marginal rate band, and the savings are larger for higher earners.
Related calculations
- Service Charge & GST Calculator: Restaurant bills in Singapore often show '++': a 10% service charge, then 9% GST on the subtotal.
- SRS Tax Savings Calculator: Shows how much tax you save by contributing to the Supplementary Retirement Scheme.
- CPF Cash Top-Up Tax Relief Calculator: Estimates the tax saved from Retirement Sum Topping-Up: up to S$8,000 for yourself and S$8,000 for family members.
- Rental (Lease) Stamp Duty Calculator: Calculates stamp duty on a tenancy agreement of four years or less at 0.4% of the total rent.
Use the Remove GST Calculator (Reverse GST) to plug in your own numbers.
Run your own numbers: Remove GST Calculator (Reverse GST)