GST registration, filing and InvoiceNow: Common mistakes and rejection reasons

GST registration, filing and InvoiceNow together govern how a Singapore business charges, reports and transmits Goods and Services Tax; missing the compulsory registration trigger, late quarterly filing, and unready e-invoicing systems are the mistakes that most often lead to IRAS penalties or rejected submissions.

What GST registration, filing and InvoiceNow are

Goods and Services Tax (GST) is Singapore’s value-added consumption tax, currently levied at 9%, administered by the Inland Revenue Authority of Singapore (IRAS) under the Goods and Services Tax Act 1993. GST registration is the process of becoming a GST-registered entity, either compulsorily once turnover thresholds are crossed or voluntarily by election. GST filing is the recurring quarterly (or in some cases monthly) return declaring output tax collected and input tax claimed. InvoiceNow is Singapore’s nationwide e-invoicing network, built on the Peppol standard, which IRAS is progressively mandating for GST-registered businesses to transmit invoice data directly for tax administration purposes.

These three pieces sit on top of the company’s underlying corporate registration with the Accounting and Corporate Regulatory Authority (ACRA): a company must first be validly incorporated and hold a Unique Entity Number (UEN) before it can register for GST, and the UEN is what IRAS uses to link GST records, InvoiceNow transmissions and the company’s income tax file together. Businesses that recently changed their registered address, business activity description or financial year end with ACRA should confirm those changes have propagated before submitting a GST registration application, since mismatches are a common cause of processing delay.

How GST registration, filing and InvoiceNow fit together

These three obligations follow a natural sequence. Registration determines whether a business must charge and account for GST at all. Filing is the recurring quarterly discipline of reporting output tax collected and input tax claimed once registered. InvoiceNow is the transmission layer that, once mandated for a given registration tier, carries structured invoice data to IRAS automatically alongside the return, reducing (but not eliminating) the manual reconciliation work involved in filing. A business that has registered but has not yet reached its InvoiceNow mandate date should still prepare early, since building the Peppol connection under deadline pressure is considerably harder than doing it with a comfortable runway.

Who needs to register, file and use InvoiceNow

This guide is for finance managers and directors of Singapore companies approaching or past the GST registration threshold, and for GST-registered businesses adapting to InvoiceNow requirements. Registration becomes compulsory when taxable turnover exceeds S$1 million over the past 12 months (retrospective view), or is reasonably expected to exceed S$1 million in the next 12 months (prospective view). Businesses below this threshold may still register voluntarily, which is common for companies with significant GST-able input costs, such as those investing heavily in fit-out or equipment before revenue ramps up. InvoiceNow-based GST reporting is being phased in progressively for newly incorporated GST-registered companies and for voluntary GST registrants from specified dates, with IRAS publishing the applicable start dates by registration tier.

Group structures also need separate assessment: each company in a group is tested against the S$1 million threshold individually, since Singapore does not currently operate group GST registration in the way some jurisdictions allow VAT grouping. A holding company with several operating subsidiaries may therefore find that some subsidiaries are compulsorily registered while others remain below the threshold and are not, which affects how intercompany charges should be invoiced and whether GST should be applied to management fees or cost recharges between related entities.

Eligibility, thresholds and requirements

Compulsory registration: taxable turnover exceeding S$1 million (retrospective 12-month test) or expected to exceed S$1 million (prospective 12-month test). Voluntary registration: available to businesses below the threshold, subject to IRAS approval and a minimum two-year registration commitment, plus the business must satisfy IRAS that it intends to make taxable supplies. Exempt supplies, such as most financial services and residential property sales, do not count toward the turnover threshold and are excluded from output tax charged, though they can restrict input tax recovery under partial exemption rules. Once registered, a business must charge GST on all taxable supplies, issue tax invoices for transactions above S$500 (or on request below that), and maintain proper records for at least five years as required under the Goods and Services Tax Act 1993 and IRAS’s e-Tax Guide on record-keeping.

Cost and timeline

GST registration via myTax Portal is processed within 10 working days for straightforward applications, longer if additional documents are requested. There is no government fee to register, but businesses typically spend S$500 to S$2,000 engaging a corporate service provider to prepare the application and set up GST-compliant accounting. GST returns are due one month after the end of each accounting period, typically quarterly, so a quarter ending 31 March must be filed by 30 April. Late filing incurs a S$200 penalty per completed month late, capped at S$10,000 per return, plus a 5% late payment penalty on unpaid tax, with a further 2% per month if the tax remains outstanding. InvoiceNow onboarding, including connecting to an accredited access point provider, typically takes 2 to 6 weeks and costs range from no additional charge (bundled with some accounting software) to a few hundred Singapore dollars a year for a dedicated access point subscription.

Numerical summary: compulsory registration threshold is S$1 million taxable turnover (retrospective or prospective 12-month test); the current GST rate is 9%; returns are due one month after each accounting period; late filing penalties run S$200 per month late up to S$10,000 per return; late payment penalties are 5% plus 2% per additional month outstanding; and voluntary registration carries a minimum two-year commitment.

Step-by-step process

First, monitor turnover monthly against the S$1 million compulsory registration threshold using the retrospective and prospective tests. Second, once liable, apply for GST registration through myTax Portal within 30 days of the liability arising, since late registration itself attracts penalties backdated to the liability date. Third, set up GST-compliant invoicing and accounting, ensuring tax invoices show the GST registration number, the 9% rate applied, and a clear split between GST-exclusive value and GST charged. Fourth, if within an InvoiceNow-mandated tier, connect an accounting system or e-invoicing solution to an accredited Peppol access point ahead of the applicable start date. Fifth, file GST returns (Form GST F5) via myTax Portal by the one-month deadline after each accounting period, reconciling output tax against sales records and input tax against purchase invoices. Sixth, pay any net GST due by the same filing deadline, using GIRO where possible to avoid processing delays. Finally, retain all tax invoices, GST reports and InvoiceNow transmission records for at least five years in case of an IRAS audit.

A practical safeguard many businesses skip is a pre-filing reconciliation step: before submitting Form GST F5, reconcile the total output tax on the return against total GST-inclusive sales for the period recorded in the accounting system, and reconcile total input tax claimed against GST-inclusive purchases recorded, checking separately for any disallowed categories that should have been excluded. This ten-minute check catches the majority of the mismatches that would otherwise surface as an IRAS query weeks or months later.

Common mistakes and rejection reasons

The most common problems in practice are: failing to register within 30 days of crossing the S$1 million threshold, resulting in backdated liability and late registration penalties even though the business believed it had more time; applying the retrospective test only and missing the separate prospective test, which can trigger registration earlier than expected; submitting GST F5 returns with input tax claimed on disallowed expenses, such as most motor vehicle costs or club subscriptions, which IRAS flags on review; under-declaring output tax by omitting GST on deemed supplies, such as gifts above S$200 or assets taken for private use; and, increasingly, InvoiceNow transmission failures where the access point connection is misconfigured or the invoice data does not match the GST return, creating discrepancies IRAS’s system flags automatically. Businesses that deregister prematurely, or fail to realise voluntary registration carries a binding two-year minimum period, also frequently run into avoidable penalties.

Directors remain personally accountable under the Goods and Services Tax Act 1993 for the accuracy of returns filed in the company’s name, even where a bookkeeper or corporate service provider prepares them. A short monthly reconciliation between sales invoices issued, GST collected, and the GST control account in the general ledger is the most effective way to catch discrepancies before they compound into a filing-period problem, particularly once InvoiceNow transmission adds a third data source that must agree with the other two.

Related guidance

For the technical clarifications IRAS issued that affect how several GST positions are now treated, see our article on IRAS’s new GST technical clarification guidelines. Businesses juggling GST compliance alongside workforce planning may find our partner site’s piece on an Employment Pass holder rejoining the same employer useful for coordinating compliance timelines across functions. For the specifics of the nationwide rollout timetable, our related article on GST InvoiceNow full roll-out (2028-2031) sets out what existing businesses need to prepare for.

FAQs

When does GST registration become compulsory?
When taxable turnover exceeds S$1 million over the past 12 months, or is reasonably expected to exceed S$1 million in the next 12 months.

Is there a fee to register for GST?
No government fee applies, though most businesses engage a corporate service provider to prepare the application and set up compliant systems.

How often must GST returns be filed?
Most businesses file quarterly, due one month after the end of each accounting period, though IRAS can assign monthly filing in some cases.

Is InvoiceNow compulsory for every GST-registered business?
It is being phased in progressively by registration tier, starting with newly incorporated and voluntary GST registrants, with IRAS publishing specific start dates rather than a single cut-off for all businesses.

What happens if a business registers for GST late?
IRAS can backdate the registration to the date the liability arose and impose penalties, including tax that should have been charged from that date, even though it was not collected from customers.

Is GST registration assessed per company or per group?
Per company. Singapore does not operate group GST registration, so each entity in a group is tested against the S$1 million threshold on its own turnover.

What is the relationship between InvoiceNow and the GST return?
InvoiceNow transmits structured invoice data to IRAS as transactions occur; it is a data channel that supports GST administration and, for mandated businesses, works alongside the periodic GST F5 return rather than replacing it.

Need help with this? Call, SMS or WhatsApp +65 8501 7133, or email [email protected]. Raffles Corporate Services works with a panel of corporate and employment law firms; this article is general information, not legal advice.