What the September 2026 FAQ covers
This article follows the IRAS FAQ dated 23 September 2026, read together with Adopting GST InvoiceNow Requirement for GST-registered Businesses. The obligation is to transmit structured invoice data to IRAS through InvoiceNow-Ready Solutions. Joining the Peppol network alone does not activate IRAS submission: without the GST InvoiceNow submission feature, customer invoices continue to circulate but are not sent to IRAS. Early activation gives businesses time to resolve integration and operational issues.
Six implementation stages
From 1 November 2025, the requirement covers companies incorporated within six months before applying for voluntary GST registration. From 1 April 2026, it covers all new voluntary registration applicants, regardless of age or constitution. From 1 April 2028, all new compulsory registrants and existing registrants with annual supplies up to S$200,000 are covered. Existing registrants above that band and up to S$1 million follow on 1 April 2029; above S$1 million and up to S$4 million on 1 April 2030; and above S$4 million on 1 April 2031. Smaller businesses are prioritised because standard accounting solutions can support relatively straightforward onboarding; larger enterprise systems need longer refresh and integration cycles.
Registration edge cases
A dormant business deregistered in 2025 but applying again voluntarily in May 2026 is covered. An April 2026 compulsory application approved voluntarily because its S$1 million forecast lacks evidence is also covered. Application date controls the first phase: an application on 31 October 2025 approved on 2 November does not enter the November first phase. A company redomiciled to Singapore is not treated as newly incorporated merely because redomiciliation occurred within six months. For these pre-April-2028 existing registrants, use the supplies-based phase; where only a short GST period ended in 2025, extrapolate to a 365-day equivalent. Where no return period ended in 2025, IRAS separately notified the mandatory date. These distinctions do not override the universal new-voluntary rule from April 2026.
Calculating the existing-business annual supplies band
Add standard-rated, zero-rated and exempt supplies in all prescribed accounting periods ending in calendar 2025. For quarterly periods ending March/June/September/December, use January–December 2025; January/April/July/October endings use November 2024–October 2025; February/May/August/November endings use December 2024–November 2025. The financial year end does not replace this GST-period test. Four nil returns still count: S$0 annual supplies place the business in the 1 April 2028 phase.
Preparing software, testing and shared ERP extensions
Check the IMDA accredited solution-provider list. An existing non-ready system can connect through an accredited Access Point, switch to a free package or migrate to an InvoiceNow-Ready solution. Custom ERP integration can be direct or through a systems integrator but still uses an accredited Access Point. A sandbox has been available since September 2024 for testing integrations and IRAS submissions. A franchise or other commercial arrangement sharing an ERP may request an extension where its date precedes the parent system’s readiness; explain the reasons and provide documents to IRAS. Extensions are assessed individually, not automatic.
Which purchases and special claims are included
Buyers submit standard-rated and zero-rated purchase data to substantiate their own purchases and input claims even if the supplier already submitted the sale; buyer data includes claim information that may differ from the seller’s data. Pre-registration input claims, bad-debt relief claims and repayment of recovered bad-debt relief are outside this invoice-data requirement, but supporting records remain necessary. A purchase from a GST-registered supplier on which no input tax is claimed is outside scope; optional transmission can simplify compliance, with category OP. This buyer exclusion does not excuse the seller from submitting an otherwise in-scope sale.
Related parties, reverse charge and overseas establishments
Principal expense recovery from a local related entity is a reimbursement supply even if settled by offsetting receivables/payables without an invoice or cash; transmit data when posted to the accounting system. Only entities registered wholly because of reverse charge on imported services and/or low-value goods are excluded on that ground; ordinary registrants that also apply reverse charge remain covered. A Singapore company with an overseas branch is not an Excluded Business. Include branch remote-service/LVG taxable supplies reported in Singapore returns; omit excluded out-of-scope supplies and non-reportable branch purchases. Related-party-only businesses, low-volume businesses and businesses wholly making zero-rated or exempt supplies cannot opt out merely for those reasons.
Peppol and solution-extracted submission routes
For Peppol submission, seller and buyer must both be on the network; activated GST submission sends IRAS a copy as the seller sends the customer invoice. Solution-extracted submission covers sales invoices issued outside the network and purchase invoices recorded in the ready solution, which transmits data periodically. Access Point Providers do not convert paper/PDF copies into Peppol invoices; record those data in the solution. Debit notes do not travel on the InvoiceNow network; for other legitimate debit-note transactions, submit data as an invoice document through solution extraction. A debit note must not replace a tax invoice for a standard-rated supply to a GST-registered business.
Aggregation, POS and duplicate copies
Transactions eligible for regular aggregation are POS sales, sales supported by simplified tax invoices or receipts, and petty-cash purchases including employee claims and corporate-card purchases. Restaurants may continue issuing POS receipts, while sending aggregated solution-extracted sales data. A business may issue paper/PDF duplicates after a Peppol invoice, but mark them as duplicate copies and prevent double input-tax claims. Cancellation documents can be transmitted as Credit Notes if they contain the required credit-note details; the supported document types are Invoice and Credit Note.
Shared service centres, agents and multiple systems
An overseas shared-service centre or authorised third-party billing provider may transmit for the business using a ready solution or an accredited Access Point; the business remains the Supplier, including its UEN in IBT-030. A provider using a ready solution needs client consent. Section 33(2) agents need not send data for their overseas principal’s self-supply to the agent or the corresponding purchase under the extended self-invoice waiver, but must invoice and transmit subsequent sales to local customers. Separate invoicing and accounting systems can remain: the submitted invoice number must match the customer-facing invoice, not the journal’s internal reference. A customer portal generating invoices for suppliers can continue; the customer submits purchase data and suppliers submit sale data via solution extraction. In-house API access requires becoming an accredited Access Point or connecting through one.
Transmission deadlines, size and acknowledgement
Type 1 A Peppol invoices generally reach IRAS in real or near-real time after successful delivery to the customer. Types 1 B, 2 and 3 solution-extracted data can be scheduled regularly, but all relevant data must arrive by the earlier of the actual GST-return filing date and its statutory filing deadline. A non-network customer’s invoices are Type 2; find network customer IDs in the SG Peppol Directory. IRAS imposes no per-field character limit or absolute line-item cap, but software interfaces may; it recommends at most 999 lines and requires XML submissions no larger than 10 MB. Providers should show date/time, status and IRAS acknowledgement ID, which confirms receipt. Keep shipping/signature and other supporting documents; they need not be attached to IRAS invoice data, but must be produced when requested.
Mandatory fields, category mapping and valid tax invoices
Collect required customer name, UEN and address even for customers outside the network. Non-GST-registered individuals may have NA for name and UEN; overseas customers use their overseas registration/identification number as UEN. Separate validation of customer-provided details is not required, but retain evidence. Missing mandatory elements cause automatic rejection. Internal tax codes may remain if mapped to the prescribed IRAS categories. A Peppol invoice without the words Tax Invoice can support input claims if all other Regulation 11 content and normal claim conditions are met. Seller and buyer categories need not match: SR for the seller can correspond to OP for a buyer unable to claim, instead of TX.
Validation against wrongful GST charges
Where implemented, the solution checks the supplier GST registration number against the IRAS registry. Type 1 A warns at issue so the supplier can correct its number or remove improper GST before issuing. Type 2 warns when sales data are submitted but submission still proceeds. Buyer Types 1 B and 3 warn when purchase data are submitted; the buyer should alert the supplier and must not claim incorrectly charged GST. The FAQ links these recommended checks to improved data quality, rather than treating a warning as confirmation that an input claim is valid.
Resubmission versus later input-tax apportionment
If the invoice record itself is amended, such as changing TX to OP, resubmit; IRAS uses the latest submission. A separate concession applies where final attribution or eligibility was unknown when purchase data were submitted: use the assessment then available and do not retrospectively adjust unchanged invoice values merely for period-end or longer-period attribution, apportionment or claim decisions. The example submits the whole S$10,000 purchase and S$900 GST using TX-RE. Retain records reconciling later tax treatment. These are different cases: the concession for unchanged invoice values does not remove the duty to resubmit an actually amended invoice record.
Credit notes, revised addresses and rejected invoices
Submit a credit note even if both parties agree not to adjust the original GST; use the original category, such as SR. A non-monetary address correction may be resent with the original Document UUID. The buyer submits only the revised record if the original was not processed; if it was submitted, resubmit the revised record and IRAS uses the latest. Rejection does not undo a seller’s Type 1 A transmission. The seller issues a network credit note, or resubmits a non-monetary correction with the original UUID. A buyer rejecting the original does not submit that original purchase; submit the credit-note/revised purchase data and claim input only on the revised eligible invoice.
Rebates, foreign currency, mixed categories and self-billing
For volume-rebate credit notes, include original invoice numbers and dates in IBT-025 and IBT-026. If a rebate cannot be linked to specific invoices, those fields may be blank, but retain evidence that GST was accounted on the original supplies. Convert all invoice data required for GST reporting, including zero-rated foreign-currency supplies, into SGD using approved GST exchange rates; the exchange rate itself need not appear in the invoice. Different line items can carry different category codes in one invoice. Self-billing is issued outside the network and transmitted by solution extraction: customer/issuer Type 3 and supplier/recipient Type 2.
GST groups and pilot lessons
GST groups continue filing consolidated returns. Invoice data may be sent by individual members or consolidated by the representative. Group-registration applications remain unchanged; a new voluntary member follows the group’s InvoiceNow phase. An Excluded Business member, such as an overseas entity, alone is excused from transmitting, not the entire group. Pilot shortcomings were missing validation, inconsistent category codes, duplicate corrective submissions and incomplete data because of system design. Configure prescribed codes, validation and version handling with providers, and check that the solution can transmit all relevant transactions.
Reconciliation, continuing obligations and enforcement
Reconcile data with returns, while documenting legitimate differences: payment-triggered time of supply or registration boundaries, deemed supplies/reverse charge without invoices, unclaimed or apportioned input, and permitted correction in F 5 rather than F 7. IRAS states businesses will not be penalised for these differences if record requirements are met and records substantiate reporting on request. Covered businesses cannot opt out; voluntary applications may be refused or registration revoked for non-compliance. Initial enforcement is calibrated for genuine mistakes not caused by negligence or lacking reasonable excuse; this is not an unrestricted penalty exemption. Remaining phases culminate in April 2031. Returns and records continue, with source documents kept at least five years, including machine-readable Peppol XML and underlying non-network invoices for audit.
Data security, grants and version history
Network safeguards include accredited Access Points with OpenPeppol PKI certificates, encrypted transport, signatures and receiver verification. IRAS describes authenticated/authorised APEX API access, encryption, role-based controls, audits, logging and monitoring, and statutory secrecy restrictions. Despite its Retention Period heading, the FAQ gives no separate IRAS retention duration; do not confuse this with the business five-year duty. As announced in this edition, SME free software is available until March 2031, a new grant up to S$1,000 will support transition, and PSG can meet up to 50% of eligible software subscriptions; larger-business early-adoption support up to S$5,000 is proposed, with details to follow. These are edition-specific support announcements, not automatic entitlements. The amendment log records October 2025, March and April 2026, and September 2026 changes, including the revised treatment of purchase adjustments and self-billing.
Official source
This article independently explains the substantive contents of the official PDF, including the relevant conditions, procedures and annexes. The linked document remains the authoritative source for its original wording, and later changes should be checked separately.
Read the official PDF ↗