GST invoice requirements Singapore: IRAS fields & formats

Key Takeaways:

• A GST tax invoice needs specific IRAS fields, and a missing field can stop your customer from claiming input tax

• Invoices of S$1,000 or less including GST can use a simplified format, and zero-rated sales follow different rules¹.

• You must keep GST invoices for at least five years¹. Use Airwallex Billing to apply the correct GST rate and calculate GST amounts automatically on your invoices.

By understanding GST invoice requirements in Singapore, you can issue compliant invoices, charge the correct GST, and keep the right records.

This guide explains when you need to issue a tax invoice, which details it must include, and when you can use a simplified format.

It also covers worked examples of standard-rated and zero-rated sales, as well as how long you need to keep your GST records.

When do you need to issue a GST tax invoice?

You generally need to issue a tax invoice when you sell standard-rated goods or services to a GST-registered customer. They need it to support their claim for input tax, so you should issue it within 30 days of the time of supply.¹

A tax invoice isn’t required for every sale. IRAS doesn’t require one for zero-rated or exempt supplies, deemed supplies, or sales to customers who aren’t GST-registered. For these customers, you can issue a receipt instead, but you must still keep proper records of the transaction.

Even when a tax invoice isn’t compulsory, you may choose to issue one for zero-rated sales to keep your records clear. See the zero-rating section below for how to document these sales.

GST invoice requirements: Mandatory fields on a tax invoice

IRAS requires specific details on every tax invoice issued to a GST-registered customer. Before sending one, check that it includes all the fields below.

• The words “Tax Invoice”

• Your business name and address

• Your GST registration number

• The invoice date

• A unique invoice number

• Your customer’s name and address

• A description of the goods or services supplied

• The applicable GST rate (9% for standard-rated supplies)¹

• The total amount payable before GST

• The total GST payable

• The total amount payable, including GST

If your invoice covers different types of supplies, show the gross amount payable for each type separately, such as standard-rated, zero-rated and exempt supplies.

What IRAS does and doesn’t require

Invoice templates often include extra details to make payments and record-keeping easier. Here’s how some common fields compare with IRAS’s requirements:

How to show your GST registration number

Your GST registration number may look different depending on your business. If it is the same as your UEN, you can label it “UEN”, “GST Reg No.” or “Company Reg No.”

If the numbers differ, use your GST registration number as provided by IRAS. Formats may include M21234567K or M2-1234567-K.¹

Invoicing in a foreign currency

If you issue an invoice in a foreign currency, you must also show the amounts in SGD for the total payable before GST, the total GST and the total payable including GST. Use an exchange rate permitted by IRAS for GST reporting.

Check the conversion carefully before issuing the invoice. These SGD amounts are important for GST reporting and help your customer determine the input tax they can claim.

Simplified tax invoice: When the S$1,000 rule applies

You can issue a simplified tax invoice when the total amount payable, including GST, is S$1,000 or less.¹ It requires fewer details than a full tax invoice, making it useful for frequent, lower-value sales.

The S$1,000 limit includes GST. For example, a sale worth S$950 before GST comes to S$1,035.50 after adding 9% GST,¹ so you would need to issue a full tax invoice if one is required.

A simplified tax invoice doesn’t show the GST amount separately. If you’re invoicing a GST-registered business, a full tax invoice makes it easier for them to identify the GST paid and support their input tax claim.

Zero-rated vs standard-rated: Examples for cross-border services

Selling to an overseas customer doesn’t automatically mean you can charge 0% GST.

Your service must qualify as an international service under Section 21(3) of the GST Act, and you must meet the relevant conditions.²

How to decide between 0% and 9%

Before applying 0% GST, check three things:

1. Where your customer belongs. Depending on the type of service, you may need to establish whether your customer belongs in Singapore or overseas.²

2. Who benefits from the service. Some provisions require the service to be contracted with an overseas person and directly benefit an overseas person who is outside Singapore when the service is performed, or a GST-registered person in Singapore.²

3. Whether the service qualifies. The service must fall within a category covered by Section 21(3) and meet its specific conditions. Simply working with an overseas customer isn’t enough.²

Example 1: Software subscription billed to an overseas client

A Singapore software company bills an overseas business customer S$2,000 for a monthly subscription. If the subscription qualifies as an international service and meets the relevant conditions, the company can charge 0% GST.

You don’t have to issue a tax invoice for a zero-rated supply. If you choose to issue one, it must show the required details and indicate that GST is charged at 0%.¹

Important: Check the GST treatment of your specific software service before applying zero-rating. The result depends on the nature of the supply and the applicable conditions.

Example 2: Marketing services billed to a Singapore client

A Singapore marketing agency charges a local client S$2,000 for a campaign. Because the service is supplied under a contract with a Singapore customer, it generally doesn’t qualify for zero-rating under the relevant international-services rules. The agency charges 9% GST.

What to keep on file

Keep your service agreement, invoices and supporting documents showing who your customer is, where they belong and what the service covers. These records can help support your GST treatment if IRAS asks you to explain it.

How to calculate GST on an invoice

If your invoice includes several standard-rated items, IRAS allows you to calculate GST in either of two ways.¹

You can calculate GST for each item and add the amounts together, or apply 9% to the combined pre-GST total. Because rounding can produce a one-cent difference, choose one method and use it consistently.

For example, suppose a customer buys three pens at S$1.28 each, before GST.¹ Here’s how you would run the calculations:

Round the total GST to the nearest cent. You can also round the final bill to the nearest five cents to facilitate cash payments, provided you apply your rounding approach consistently.¹

Airwallex Billing supports automatic tax calculation on invoices and subscriptions for supported tax jurisdictions and configurations, helping reduce manual calculations. Check that your required tax treatment is supported before relying on the feature.

Common GST invoice mistakes to avoid

A missing detail or incorrect GST calculation can cause problems for both you and your customer. Use this checklist to catch common mistakes before you send an invoice:

• Leaving out “Tax Invoice”. A full tax invoice must display these words prominently. Labelling it simply “Invoice” doesn’t meet this requirement.¹

• Missing customer details. A full tax invoice must include your customer’s name and address. Don’t leave these fields blank or replace them with a generic label such as “Cash”.¹

• Forgetting SGD amounts. If you invoice in a foreign currency, you must also show the total before GST, the GST amount and the total including GST in SGD, using an exchange rate approved by IRAS.¹

• Combining different types of supplies. If an invoice includes standard-rated, zero-rated or exempt supplies, state the gross amount payable for each type separately.¹

• Changing how you calculate GST. IRAS accepts two methods for calculating GST across multiple standard-rated items. Choose one and apply it consistently to avoid discrepancies caused by rounding.¹

• Using a simplified tax invoice for a larger sale. You can use the simplified format only when the total amount payable, including GST, is S$1,000 or less.¹

• Issuing a tax invoice late. You generally need to issue a tax invoice within 30 days of the time of supply.¹

How long to keep GST invoices in Singapore

You must keep the tax invoices you issue to customers and those you receive from suppliers for at least five years. You don’t need to submit them with your GST returns.¹

Tax invoices are important records for supporting input tax claims, so keep both sales and purchase invoices organised and easy to retrieve.

You’ll need to produce them if IRAS asks to review your GST records. The five-year retention period runs from the end of the relevant accounting period.¹

InvoiceNow and GST invoices: What changed in 2026

Singapore is phasing in a requirement for GST-registered businesses to transmit invoice data to IRAS through InvoiceNow, the nationwide e-invoicing network. Businesses must use an InvoiceNow-Ready Solution to submit the data.¹

The first phases apply to businesses registering for GST voluntarily:

• From 1 November 2025: Newly incorporated companies applying for voluntary GST registration within six months of incorporation.

• From 1 April 2026: All new voluntary GST registrants, regardless of incorporation date or business structure.¹

In 2026, IRAS also announced a phased rollout for other GST-registered businesses, starting in April 2028 and continuing through April 2031. The implementation date depends on the business’s registration status and annual supplies.²

If the requirement applies to your business, check that your software supports InvoiceNow data transmission to IRAS. You must still meet your existing GST invoicing and record-keeping obligations. For details, read our guide to InvoiceNow.

InvoiceNow and GST invoices: What changed in 2026

Singapore is phasing in a requirement for GST-registered businesses to transmit invoice data to IRAS through InvoiceNow, the nationwide e-invoicing network. Businesses must use an InvoiceNow-Ready Solution to submit the data.¹

The first phases apply to businesses registering for GST voluntarily:

• From 1 November 2025: Newly incorporated companies applying for voluntary GST registration within six months of incorporation.

• From 1 April 2026: All new voluntary GST registrants, regardless of incorporation date or business structure.¹

In 2026, IRAS also announced a phased rollout for other GST-registered businesses, starting in April 2028 and continuing through April 2031. The implementation date depends on the business’s registration status and annual supplies.²

If the requirement applies to your business, check that your software supports InvoiceNow data transmission to IRAS. You must still meet your existing GST invoicing and record-keeping obligations. For details, read our guide to InvoiceNow.

Generating compliant invoices automatically

Airwallex Invoicing can help you reduce repetitive invoicing work:

• Create and manage invoices: Generate and send invoices without rebuilding a template each time.

• Automate tax calculations: Configure Automatic Tax Calculation to calculate and apply tax to eligible invoices and subscriptions, based on your tax registrations, product categories and customer details.

Airwallex also supports invoicing in 130+ currencies, with online invoice payments available through supported payment methods. This lets you easily bill overseas customers.

You can sign up for an Airwallex Business Account fully online. There are no setup fees, monthly fees, or minimum balance requirements on the free Explore plan.

Frequently asked questions

What must a GST invoice include in Singapore?

IRAS requires 12 items on a standard tax invoice.¹ They include the words “Tax Invoice”, your GST registration number, the invoice date, the customer’s name and address, the GST rate, and the totals excluding and including GST. See the mandatory fields checklist above for the full list. Airwallex Invoicing adds the correct tax fields automatically.

Is a UEN required on a Singapore tax invoice?

No. IRAS lists your GST registration number as a mandatory invoice field, not a separate UEN. If your UEN is also your GST registration number, you can show it under a label such as UEN or GST Reg No.

What is a simplified tax invoice, and when can I use one?

A simplified tax invoice is a shorter version you can issue when the total amount payable, including GST, is S$1,000 or less.¹ It needs fewer fields, but it must still carry a statement that the price payable includes GST.

Do I need to issue a tax invoice for zero-rated sales?

No. IRAS says you don’t need to issue a tax invoice for zero-rated supplies, exempt supplies, deemed supplies, or sales to customers who aren’t GST-registered. If you do issue one, state the zero-rated amount separately from any standard-rated items.

Do I charge GST on services to overseas clients?

Not always. Services to overseas customers are zero-rated only if they meet the international services rules in Section 21(3) of the GST Act. IRAS stresses that not all services provided to overseas customers qualify.² Check your service and your customer against those rules before you choose a rate.

How long must I keep GST invoices in Singapore?

Keep them for at least five years.¹ This covers the tax invoices you issue and the ones your suppliers give you. You don’t need to submit them with your GST returns.

Sources:

1. https://www.iras.gov.sg/taxes/goods-services-tax-(gst)/basics-of-gst/invoicing-price-display-and-record-keeping/invoicing-customers

2. https://www.iras.gov.sg/taxes/goods-services-tax-(gst)/charging-gst-(output-tax)/when-to-charge-0-gst-(zero-rate)/providing-international-services

3. https://www.iras.gov.sg/taxes/goods-services-tax-(gst)/specific-business-sectors/advertising

4. https://www.iras.gov.sg/taxes/goods-services-tax-(gst)/gst-invoicenow-requirement