Why Did a S$5.50 Purchase Appear as US$4.27?

A receipt in Singapore showed S$5.50, while a U.S. credit-card account displayed only US$4.27. Another purchase of about S$48 appeared as roughly US$38. A bank-card transit ride also failed to appear immediately as pending.

Author: Koutian Wu; GitHub: ktwu01

This looked like three problems. Had the merchant skipped GST? Had the bank omitted part of the charge? Had the transit fare disappeared?

The explanation combines three systems: currency conversion, tax-inclusive pricing, and delayed transit settlement.

S$5.50 is not US$5.50

Singapore dollars and U.S. dollars both use the “$” symbol. Singapore receipts use SGD, while U.S. credit-card accounts normally display USD.

The implied exchange rate in this example is approximately:

[ 5.50\ \text{SGD} / 4.27\ \text{USD} \approx 1.288\ \text{SGD/USD} ]

Therefore, S$5.50 converts to about US$4.27, while S$48 converts to about US$38. The bank did not omit or split the charge. It converted the merchant’s Singapore-dollar amount into the account’s U.S.-dollar billing currency.

If the card carries no foreign transaction fee, no additional percentage fee should appear.

GST was already inside the S$5.50 price

GST means Goods and Services Tax. Singapore’s prevailing GST rate is 9%.

U.S. consumers often see sales tax added at checkout. Singapore generally uses tax-inclusive consumer pricing. Under the IRAS price-display requirements, GST-registered businesses must display GST-inclusive prices to the public.

For a final price of S$5.50:

[ \text{Pre-GST price}=5.50/1.09\approx S$5.05 ]

[ \text{GST}=5.50-5.05\approx S$0.45 ]

The S$5.50 total therefore contains about S$5.05 before tax and S$0.45 of GST. The card issuer then converts the complete S$5.50 into approximately US$4.27. GST does not become a separate card transaction.

“Not subject to GST” may not apply to the entire order

Some receipts print:

*Not subject to GST

The asterisk is often a footnote marker that applies only to marked lines, not the whole order. Free customizations may be labeled FOC, meaning Free of Charge, and marked as not subject to GST. Those zero-value lines generate no tax, while the paid main item remains taxable.

To determine whether an order includes GST, inspect the paid item, total, and fields such as “Incl GST 9%,” rather than relying on a footnote alone.

What is a GST Reg No.?

A GST Reg No. is a merchant’s GST Registration Number.

It is neither the tax amount nor the order number. It identifies the registered entity responsible for collecting and reporting GST. Registration status can be checked through the IRAS GST Registered Business Search.

Before sharing a receipt publicly, redact the GST registration number, merchant name, order number, timestamp, location, QR code, and payment credentials.

Why had the transit charge not appeared as pending?

Singapore’s bank-card transit system uses account-based ticketing. Readers first record taps; the system later calculates distance-based fares and submits settlement. A transit charge may therefore appear later or combine multiple journeys.

The SimplyGo App provides journey and payment records for linked cards. Riders should also use the same payment medium for entry and exit: a physical card and the same card in a mobile wallet may be treated as different credentials.

Conclusion

• Singapore receipts normally use SGD
• U.S. credit-card accounts normally use USD
• Singapore consumer prices generally include 9% GST
• The bank converts the tax-inclusive amount into U.S. dollars
• Transit charges may settle later or combine multiple rides

A S$5.50 purchase appearing as US$4.27 is not a discount, omitted charge, split transaction, or tax loophole.

It is an ordinary transaction made confusing by two currencies that share the same symbol, tax-inclusive pricing, and delayed settlement.