Singapore GST Calculator: How GST Is Calculated in 2026 (9% Rate)

The math is simple. The mistakes are not. We've seen plenty of Singapore SMEs lose money on every invoice because they forget the difference between adding GST to a net price and extracting GST from an inclusive one. Or because their software is set to the wrong rate. Or because they apply the discount in the wrong order.

This guide gives you the formulas, the reference tables, and worked examples for every situation an SME encounters: invoicing in SGD, quoting GST-inclusive, mixed standard and zero-rated supplies, discounts, and foreign currency.

The current Singapore GST rate

Singapore's GST rate is 9%, effective from 1 January 2024. This applies to all standard-rated supplies of goods and services. Zero-rated supplies (exports, qualifying international services) remain at 0%; exempt supplies (residential property rental, certain financial services, digital payment tokens, investment-grade precious metals) carry no GST.

Source: IRAS Current GST rates.

The two formulas you actually need

To add GST to a net (exclusive) price: multiply by 1.09.

GST amount = net × 0.09
GST-inclusive total = net × 1.09

To extract GST from an inclusive price: divide by 1.09.

Net amount = inclusive ÷ 1.09
GST amount = inclusive × 9/109

The fraction 9/109 is what IRAS calls the tax fraction. It's the cleanest way to extract GST from a GST-inclusive figure without losing cents to rounding.

Quick reference tables

Adding 9% GST to common amounts

Extracting GST from common GST-inclusive amounts

Five worked scenarios

1. Invoice from a S$100 net price

You're a GST-registered SME quoting S$100 for a service.

• GST: S$100.00 × 0.09 = S$9.00
• Total payable: S$109.00

Show it on the invoice as: Service S$100.00, GST 9% S$9.00, Total S$109.00.

2. Working backwards from a S$109 GST-inclusive quote

A customer asks for the GST breakdown on a S$109 quote.

• Net: S$109.00 ÷ 1.09 = S$100.00
• GST: S$109.00 × 9/109 = S$9.00

3. Mixed standard-rated and zero-rated on one invoice

You're billing a customer for local consulting (standard-rated S$1,000) and exported goods (zero-rated S$500).

In your GST F5 return, standard-rated supplies are S$1,000 with output tax S$90; zero-rated supplies are S$500. For more on cross-border zero-rating, see our GST for foreign clients guide.

4. Discount applied before GST

List price S$1,000, 10% discount, then GST.

1. Discount: S$1,000 × 10% = S$100
2. Net after discount: S$900.00
3. GST: S$900.00 × 0.09 = S$81.00
4. Total payable: S$981.00

The discount is applied before GST is calculated. If you give the discount after GST has been charged (e.g. a post-sale rebate), you adjust the GST by issuing a credit note that reduces both the value of supply and the GST.

5. Foreign currency invoice

You bill a US client US$1,000 for a standard-rated service. The exchange rate at time of supply is US$1 = S$1.35.

1. SGD equivalent: 1,000 × 1.35 = S$1,350.00
2. GST: S$1,350.00 × 0.09 = S$121.50

You report S$121.50 as output tax in your GST F5 return. IRAS requires you to convert to SGD at the time of supply using a reasonable, consistently-applied exchange rate (your bank's rate or an IRAS-approved rate).

What a compliant tax invoice must show

Once you've done the calculation, the invoice itself needs to meet IRAS's tax invoice requirements. The mandatory fields:

• The words "Tax invoice" clearly visible
• Your business name, address, and GST registration number
• Invoice number and date of issue
• Customer's name and address
• Description, quantity, and amount of each item
• Total amount payable excluding GST
• The rate and amount of GST (and the indicator "0%" for zero-rated items)
• Total amount payable including GST

For receipts under S$1,000 issued to customers, a simplified tax invoice with fewer fields is permitted. From 1 April 2026, new voluntary GST registrants must additionally transmit invoice data via InvoiceNow (Peppol); see our voluntary GST registration guide.

IRAS rounding rules

Round GST amounts to the nearest cent (0.5 cent rounds up). You can round per line item or per invoice total, provided you apply the method consistently. The difference between methods should not exceed ±1 cent.

In Xero and most modern accounting software, the default is line-by-line rounding; pick one and stick with it.

When prices must be displayed GST-inclusive

Singapore consumer law requires consumer-facing prices to be GST-inclusive. You may show the GST-exclusive figure additionally, but the GST-inclusive total must be at least as prominent. For B2B contexts, GST-exclusive pricing is permitted as long as you clearly label it (e.g. "S$10,000 before GST").

The "++" pricing convention in F&B and hotels (price + service charge + GST) is allowed, but the final GST-inclusive figure must still be communicated clearly before payment.

Common SME GST calculation mistakes

These are the ones IRAS audits frequently catch:

1. Inconsistent rounding. Per-line one month, per-invoice the next, creating cumulative errors over the quarter.
2. Double-counting GST on inclusive prices. Treating a S$109 inclusive price as net and adding 9% again, ending up at S$118.81. Decide whether your base figure is net or gross, then apply the right formula.
3. Old rate still in templates. Invoices from old systems still showing 7% or 8% after the rate changes. For any supply on or after 1 January 2024, the rate is 9%.
4. Misclassifying supplies. Zero-rated and exempt are not the same. Zero-rated lets you claim input tax; exempt does not. Out-of-scope supplies don't go into the GST return at all.

Frequently asked questions

What's the current Singapore GST rate?

9%, effective from 1 January 2024 (IRAS confirmation). The previous rate was 8% (from 1 January 2023 to 31 December 2023), and before that 7% (until 31 December 2022).

How do I calculate GST on an inclusive price?

Divide the inclusive price by 1.09 to get the net amount, then subtract to get the GST. Or use the tax fraction 9/109 directly: GST = inclusive × 9/109.

Do I have to register for GST as a small business?

Compulsory registration kicks in when your taxable turnover exceeds S$1 million. You can also register voluntarily before that threshold; see our voluntary GST registration guide for when it's worth it and our GST registration timing guide for the threshold tests.

How often do I file GST returns?

Most GST-registered businesses file Form GST F5 quarterly (within one month of each accounting period end). IRAS can approve different filing periods on application, but quarterly is the standard.

Does GST apply to my exports to overseas customers?

Exports of goods and qualifying international services are zero-rated; you charge 0% output GST but can still claim input tax on related costs. See our foreign clients guide for the documentation requirements.

GST calculation is fast once your accounting system is set up properly. The pain comes from inconsistent application across hundreds of transactions a quarter. Xero software solves this problem and the GST F5 can be submitted directly through the software further eliminating manual error. Book a free consultation with us to get set up. We handle GST filings with Xero for Singapore SMEs every quarter, and the calculations happen automatically with the right tax codes in place.