Singapore GST on Foreign-Currency Invoices: Which Exchange Rate IRAS Accepts

A GST-registered business in Singapore can invoice in US dollars, euros or any other currency. The tax invoice still has to carry Singapore dollar figures, and IRAS sets out where the exchange rate may come from and how consistently it must be applied. The rules are in the GST Act, the GST (General) Regulations and the IRAS e-Tax Guide "GST: Exchange Rates for GST Purpose" (fourth edition, 30 January 2026).

What must be shown in Singapore dollars

IRAS requires three amounts on a foreign-currency tax invoice to be converted into Singapore dollars:

• the total amount payable excluding GST,
• the total GST payable, and
• the total amount payable including GST.

Regulation 11 of the GST (General) Regulations is the source of the requirement. The Singapore dollar figures on the invoice are what go into Box 1 and Box 6 of the GST return.

Which rate, on which date

The Third Schedule to the GST Act refers to the selling rate of exchange prevailing in Singapore at the time when the supply takes place. In practice the e-Tax Guide is wider: the daily exchange rate may be the prevailing buying rate, the selling rate or the average of the two, and it is acceptable to approximate the rate at the time of supply with:

• the rate on a particular day of the month, such as the last working day of the previous month, or
• an average over a specific period, such as the average of the daily rates for the previous month.

Sources IRAS accepts without approval

• Local banks: full banks, wholesale banks, offshore banks and merchant banks in Singapore.
• The Monetary Authority of Singapore (MAS).
• Locally circulated newspapers: Business Times, Straits Times, Financial Times and Lianhe Zaobao.
• Reputable news agencies: IRAS names Bloomberg, Reuters and Oanda.
• Foreign central banks without exchange controls: the guide gives the European Central Bank and the Federal Reserve Bank of New York as examples.
• Online resources are acceptable if they obtain their rates from the sources above.

The three conditions

Using a listed source is not enough on its own. The guide sets conditions that all have to be met:

1. The exchange rate is updated at least once every three months.
2. The exchange rate is used consistently for internal business reporting, accounting and GST purposes.
3. The exchange rate is used consistently for at least one year from the end of the accounting period in which the method was first used.

A business that meets them does not need to seek the Comptroller's approval.

In-house rates

A business that wants an in-house rate based on other sources, or that cannot meet all the conditions, has to seek the Comptroller's approval in writing through myTax Mail. The application includes a comparison of the in-house rate with the listed sources over a two-week period. IRAS says it will generally allow rates that are close approximations of the listed ones.

The buyer's side

The customer claims input tax on the Singapore dollar GST amount the supplier put on the tax invoice, not on a figure converted at the customer's own book rate. For imports, input tax is claimed on the Singapore dollar amounts shown in the import permit. Realised exchange gains and losses are reported net in Box 3 as exempt supplies.

Getting the MAS rate for an invoice date

MAS releases its rates at 3 pm on each business day for 21 currencies, describing them as the average of buying and selling interbank rates quoted around midday in Singapore. The API returns the table for today or for any past date:

# today's MAS table
curl "https://allratestoday.com/api/open/central-bank/mas"

# the MAS table for an invoice date
curl "https://allratestoday.com/api/v1/central-bank/mas/2026-09-30" \
  -H "Authorization: Bearer YOUR_API_KEY"

# a month of daily USD rates as CSV, for a monthly average policy
curl "https://allratestoday.com/api/v1/central-bank/mas/history?symbol=USD&from=2026-10-01&to=2026-10-31&format=csv" \
  -H "Authorization: Bearer YOUR_API_KEY"

The dated response includes requested_date and rate_date. For a weekend or a public holiday, rate_date shows the earlier table that was returned. On 11 November 2026 the MAS rates were S$1.2819 to the US dollar, S$1.4309 to the euro and S$1.7106 to sterling. Dated tables and history are on paid plans.

A policy that satisfies the conditions

1. Pick one listed source, for example the MAS rate on the last business day of the previous month.
2. Write it into the accounting policy and use the same rate for books and GST.
3. Refresh it at least every three months; monthly is simpler.
4. Keep it for at least a year before changing.

This guide describes the rules as IRAS, Singapore Customs and MAS publish them, read on 11 November 2026. It is not tax advice; confirm the treatment for your facts with your tax agent.

FAQ

Which exchange rate does IRAS accept for GST?

Rates from local banks, MAS, locally circulated newspapers, reputable news agencies and foreign central banks without exchange controls. The rate must be updated at least every three months, used consistently for books and GST, and kept for at least one year.

What must a foreign-currency tax invoice show in Singapore dollars?

Three amounts: the total payable excluding GST, the total GST payable and the total payable including GST.

Do I need IRAS approval for my exchange rate?

Not if the rate comes from a listed source and all the conditions are met. An in-house rate based on other sources needs the Comptroller's approval, requested through myTax Mail with a two-week comparison.

Which date's rate applies to a GST invoice?

The rate at the time of supply. IRAS accepts an approximation, such as the rate on a fixed day of the month or an average for the previous month, if it is applied consistently.