IRAS Makes InvoiceNow a Legal Condition for GST Voluntary Registration

The Inland Revenue Authority of Singapore (IRAS) has issued a new e-Tax Guide on 30 January 2026, formalizing the conditions for Goods and Services Tax (GST) voluntary registration that now carry the force of law.

For accountants and finance professionals, the most critical takeaway is the elevation of digital infrastructure to a statutory compliance requirement.

The New Compliance Threshold
Effective immediately, businesses that are GST-registered on a voluntary basis must adhere strictly to the conditions outlined in the guide. Failure to comply risks cancellation of their GST registration . While the guide covers standard eligibility criteria, the spotlight falls squarely on the GST InvoiceNow Requirement.

Mandatory E-Invoicing Deadlines
IRAS has confirmed that compliance with the InvoiceNow regime is now a binding condition for voluntary registrants, tied to a strict phased schedule . The deadlines are as follows:

• From 1 November 2025: Applicable to companies that register for GST voluntarily within six months of being incorporated .

• From 1 April 2026: Mandatory for all new voluntary GST registrants, irrespective of their incorporation date or business constitution .

Practical Impact
For Tax Accountants advising clients on voluntary registration, the practical implications are significant. Businesses must utilize InvoiceNow-ready solutions (accounting software or in-house enterprise resource planning systems connected via the Peppol network) to transmit invoice data directly to IRAS .

Operational Risks
From an audit perspective, the key risk lies in data transmission deadlines. Invoice data must be transmitted to IRAS by the earlier of the actual GST return filing date or the statutory filing due date . Late transmission, even if the return is filed on time, could technically constitute a breach of registration conditions.

Furthermore, the quality of master data is now a compliance issue. By May 2026, technical validations (such as requiring a Universally Unique Invoice Identifier) will become stricter, meaning that formatting errors could lead to invoice rejection and subsequent gaps in IRAS audit trails .

Exclusions and Practical Hurdles
While overseas entities and businesses registered solely under the Reverse Charge regime are excluded, most local small and medium-sized enterprises pursuing voluntary registration will be captured by this mandate . Accountants should note that relying on basic, non-digital invoicing methods is no longer an option for this segment.

Recommendation
Tax Accountants should immediately review any pending or recent voluntary registration applications to ensure the client’s accounting system is InvoiceNow-compatible. With onboarding lead times potentially extending to several months for complex setups, early technical assessment is now a matter of tax compliance, not just operational efficiency.