When is your GST InvoiceNow implementation date? Singapore is phasing in a requirement that changes what a GST invoice is. Under the IRAS GST InvoiceNow requirement, GST-registered businesses transmit invoice data to IRAS in structured form over the nationwide InvoiceNow network — built on the international Peppol standard — rather than only issuing documents to their customers. The question that matters is not whether this applies to you, but when. The phased timeline The requirement arrives in stages. From April 2026 it applies to newly incorporated companies that register voluntarily for GST. IRAS is notifying existing GST-registered businesses of their individual implementation dates, and the requirement extends progressively until it covers all GST-registered businesses — the announced rollout runs to April 2031. Your date depends on your registration circumstances: IRAS publishes an implementation date calculator, and checking it takes minutes. Transitional support is available for early adopters. What actually changes Invoice data leaves your accounting or ERP system in structured form and reaches IRAS through the InvoiceNow network. The data has to be complete at the source: customer and supplier identifiers, registration data and invoice fields that a person quietly fixed on a printed document must now be right in the system. The transmission pathway becomes part of your compliance position — a rejected or failed transmission is an exception someone must own and resolve. And the evidence trail matters: what was transmitted, when, and how it reconciles to the ledger. Why early movers have the easier project The businesses that treat GST InvoiceNow readiness as a data-quality project — rather than a last-minute connector purchase — fix their master data on their own schedule instead of under a deadline. The failure mode is predictable: a transmission pathway switched on above incomplete data automates the production of wrong submissions. The readiness test Four questions tell you most of what you need to know: Does your GST configuration produce the right posting outcome for every transaction type you run? Do your customer and supplier records carry the identifiers a structured invoice requires? Can an invoice leave your system without anyone editing it first? When a transmission fails, does the exception land in an owned workflow or an inbox? If any answer is no, the readiness work is real — and it is measurable, boundable and fixable ahead of your implementation date. If you run Business Central For Microsoft Dynamics 365 Business Central estates, readiness maps onto the platform's e-document capability and a Peppol-ready access point — and onto the configuration and master data underneath it. INFOC runs this as a fixed-scope readiness assessment: you leave with a documented gap map, an approved design and a tested position, not a sales pitch.