All GST-registered businesses in Singapore, phased as above. Supply AND purchase invoice data must be transmitted, including invoices issued outside the InvoiceNow network (paper/PDF/POS) once recorded in the InvoiceNow-Ready Solution. Phase allocation for existing registrants is fixed by total annual supplies (GST return Box 4) in all prescribed accounting periods ending in calendar year 2025, extrapolated to 365 days if short. EXCLUDED: overseas entities required to appoint a s.33(1) local agent, and Overseas Vendor Registration (OVR) Pay-only and full-regime registrants; and businesses liable to register for GST solely by virtue of the reverse-charge / low-value-goods rules. A foreign-incorporated company WITH a Singapore branch is not excluded.
This is a 5-corner REPORTING obligation, not just e-invoicing — you must transmit PURCHASE invoice data too, and supply invoices issued outside the network (PDF, paper, POS) once they are recorded. Your phase is locked to CY2025 supplies, so a business's 2028–2031 date is already determined by numbers it has already filed; IRAS said it would notify pre-2026 registrants of their date by mid-2026. Voluntary registrants are the sharp end: from 1 Apr 2026 InvoiceNow is a CONDITION of voluntary GST registration and non-compliance can have registration revoked. Beware secondary sources (e.g. some vendor 'regulations' pages) asserting the mandate is already fully in force for every GST-registered business — that flatly contradicts the IRAS e-Tax Guide.
4 of 6 are primary sources. Mandate dates move — treat this page as a starting point and confirm against the primary source before committing a plan.
A page is a starting point. A scoped analysis gives you the specification, the mapping and the effort — in weeks, not quarters.
