As we close the books on 2025, successful business owners face a “happy problem”: High Revenue.

But in Singapore, hitting the S$1 million revenue mark triggers a major compliance obligation: Mandatory GST Registration.

Many directors assume they can “wait and see.” However, IRAS strict rules mean you could face penalties if you miss the registration window by even one day.

In this guide, we explain how to calculate your threshold and—crucially—the new InvoiceNow requirement that affects new registrants from late 2025 onwards.

1. The Magic Number: How to Check if You Must Register

You are liable to register for GST if you meet either of these two conditions.

A. The Retrospective View (The “Look Back”)

Look at your accounts on 31 December 2025.

  • Question: Did your taxable turnover (sales) exceed S$1 million in the calendar year (1 Jan 2025 – 31 Dec 2025)?

  • Action: If YES, you must apply for registration by 30 Jan 2026.

  • Result: You will be GST-registered starting 1 March 2026.

B. The Prospective View (The “Look Forward”)

  • Question: Do you reasonably expect your turnover to exceed S$1 million in the next 12 months? (e.g., You just signed a single contract worth $1.2M).

  • Action: You must register immediately (within 30 days of signing that contract).

2. The New 2025/2026 Rule: Mandatory “InvoiceNow”

If you are planning to register for GST (especially Voluntarily) to claim back input tax, you must be aware of the new digitalization mandate.

From 1 November 2025, IRAS requires newly incorporated companies that register for GST voluntarily to transmit their invoice data via InvoiceNow.

What is InvoiceNow?

It is not just emailing a PDF. InvoiceNow is a nationwide E-invoicing network (Peppol) where invoices are sent directly from one accounting software (like Xero or Quickbooks) to another.

  • The Change: You can no longer just “create a manual invoice in Word.” You must use Accounting Software that is “InvoiceNow-Ready.”

  • The Timeline:

    • 1 Nov 2025: Mandatory for new companies (incorporated <6 months) registering voluntarily.

    • 1 April 2026: Mandatory for ALL new voluntary GST registrants.

3. What If I Register Late? (The Penalties)

If you crossed the $1M mark in June but forgot to register until December, you are in trouble. IRAS can impose:

  1. Backdated Taxes: You must pay the 9% GST on all sales from the date you should have been registered (even if you didn’t collect it from clients!).

  2. 10% Penalty: A penalty of 10% on the GST due.

  3. Fine: A fine of up to S$10,000.

4. Should I Register Voluntarily? (Revenue <$1M)

If you earn less than $1 million, you can choose to register voluntarily.

  • Pros: You can claim back the GST you pay on rent and office equipment.

  • Cons: You must stay registered for at least 2 years, and you must comply with the new InvoiceNow rules.

Conclusion: Don’t Guess Your Revenue

GST is complex. Calculating “Taxable Turnover” isn’t just adding up bank deposits (e.g., sale of capital assets or inter-company loans might be excluded).

At Excellence Singapore, our Accounting & Taxation Team can perform a GST Liability Assessment for you. We check:

  1. If you have hit the threshold.

  2. If you can apply for “Exemption” (if your supplies are mostly zero-rated).

  3. If your software is ready for the new InvoiceNow mandate.

Avoid the 10% penalty. Contact us to review your GST status before 31 Dec