Ask a business owner why IRAS compliance matters, and you’re likely to hear “so we don’t get fined”. While that is correct in one sense, it’s only part of the story and probably why many businesses still think of tax compliance as a quarterly burst from the accounting team rather than part of how the entire business operates daily. Things are changing though, rapidly so.
IRAS is transitioning Singapore's GST framework from a quarterly, self-assessed filing process to real-time, structured data from invoice creation.
To a business still piecing together a quarterly GST calculation by hand, this is more than a policy footnote, and warrants a review of how the company actually creates invoices, processes them, and accounting is actually managed, not simply whether the monthly return is in.
What IRAS actually oversees, and what it doesn't
And to be precise for a moment, many Singapore companies confusingly consider the “whole world” to be IRAS whereas in fact, while they’re part of “compliance”, they are one of several different regulators. The IRAS deals with corporate income tax, GST and withholding tax. ACRA manages company incorporation, annual returns and annual AGMs, while the CPF Board administers employee CPF contributions (albeit the employment income data is routed through IRAS via Auto-Inclusion Scheme) - separate regulators, with separate schedules, separate penalties. It is absolutely possible for a company to be completely compliant with ACRA and yet dangerously behind with IRAS (or the other way round).
For corporate tax, two fixed obligations of a Singapore registered company (big or small, profitable or not) are due every year: submit Estimated Chargeable Income (ECI) with 3 months after financial year end and a final tax return (form C-S, C-S Lite or C) with 30 November in the next calendar year. Singapore's corporate tax rate is a flat 17%, although thanks to the Partial Tax Exemption and Start-Up Tax Exemption provisions, most companies actually end up paying rather little tax for the first chunk of profit. And for Y/A 2026 (e.g. Tax for the Year of Assessment for accounting periods closed as at 31 Dec 2025), those with actual taxes payable get a 40% CIR up to $30k on their tax payable with a separate cash grant to qualifying companies hiring any locals in 2025. There’s no ERP or special system software required for these fixed tax-related deadlines - just a diligent director – as directors retain personal responsibility for the submission despite engaging a tax agent.
It is where GST becomes the game with slightly higher operational stakes. Once annual taxable turnover exceeds $1M in a rolling 12 months, you are required to be registered for GST. Once registered, you collect 9% GST from your customers on qualifying sales and you will declare what GST you collected against any GST you paid when you file your returns, usually on quarterly intervals. Failing to file automatically incurs a penalty and late payment of the GST itself adds a surcharge, rising at 5% per annum.GST filing represents that part of IRAS compliance where you hit your operating system, not just annually, hence naturally this is the most impacted item from what’s following.
The real shift: GST InvoiceNow and what it changes
Traditionally, GST compliance meant good bookkeeping inside the business, and submitting the summary totals to IRAS periodically. What went to IRAS was the total amount; how that total was arrived at was pretty much that business's problem until IRAS made inquiries. The GST InvoiceNow Requirement alters that relationship.
InvoiceNow requires GST-registered firms to deliver invoice data in a specified structured format (based on the PINT-SG format which rides on the international Peppol framework) to IRAS through an accredited Access Point service provider – rather than rely on IRAS receiving total amounts in quarterly returns. The introduction has been staggered: an early adoption voluntary option opened mid-2025, new GST-registered companies that were filing voluntarily came on-stream in November 2025, all new GST registrants were then required to come onto it from 1 April 2026 and now existing GST registrants will be onboarded in stages from April 2028 to April 2031, when it will be mandatory for all GST-registered companies.
In practice this means that gst compliance is no longer just a case of the total on the returns matching good internal records. GST compliance means that, at the time an invoice exits the business, it should be structured with the correct GST rate (inclusive of whether it is a no-supply and the correct tax type such as “STANDARD RATED / ZERO RATED / exempt with input tax claim” used) and other tax identifiers (e.g. Harmonized Commodity Description and Packaging Code (HSN) or CPVC); the systems that generate it will directly provide those details to IRAS. In other words, where, in the past, a business had got the occasional GST treatment wrong on invoices and compensated for that at the quarter end prior to submission, such flexibility to correct at the last moment is eroded as invoice data is provided to IRAS directly in a consistent, standardized format on creation.
This is also why the question of compliance is increasingly a " systems" issue, rather than a pure finance operations issue. Companies now need to consider the systems' capability to not only provide reporting that looks good end-of-quarter but also to be able to, generate InvoiceNow-compatible invoice data accurately on thefly.
Where this actually bites, in practice
A growing SME nearing the $1 million GST threshold The current general view by many is that GST registration is still something that is on the horizon for them. However, in practical terms, as soon as you reach the $1m threshold, you will need the GST-compliant invoices from day one of GST registration, and if you are a newly voluntary registered company on/after 1 Apr 2026, invoice now becomes compulsory as the system will flag an application without it to the IRAS for validation/approval even before approving a registration. And for a newly registered company that did not verify that its systems are compatible with this system when it comes to registering for GST, will be running around putting out fires post-registration.
A multinational's Singapore subsidiary, which is already GST registered. These companies are not in a hurry to beat the 2026 deadline (for new voluntary registrants), but they will be reminded when their scheduled date is under the 2028 to 2031 rollout, depending on when their taxable supply exceeds the amount designated by Inland Revenue. However, it’s awfully tempting to just push this date to the future, since it’s not immediate for them. In our experience, the companies that face the most difficulty when their InvoiceNow mandate date approaches are those who didn’t have their GST tax codes properly documented, since properly doing this takes some effort.
E-commerce company issuing invoices daily An e-commerce company and there are a lot of invoices being churned out everyday by the accounting department. Manual input errors are greatest when invoice-level is huge and this is also where a fully set up, ready-for-InvoiceNow, accounting solution has its case. The other approach is a manual review of the GST treatment of each invoice volume which will be near impossible.
A multi-entity group with multiple UENs, each entity with its own GST status, its own filing due dates and (at some future date) a unique InvoiceNow go-live date. Group finance teams attempting to run this at a consolidated level with no sensible method of tracking entity specific due dates are by far the most likely to incorrectly report an entity deadline as being met.
Where compliance quietly breaks down
The entities that actually get fined are almost never entities that don't know GST / Corporate tax on a conceptual level. It's almost always a process failure. Director thinks his engaged tax agent have done it while the responsibility of timely filing and accountability lies with the director. Finance team reconciles GST manually on a quarterly basis and occasionally mismatches an invoice line under a time crunch – this will always be excusable when only a sum matters; definitely much less so when IRAS has all the invoice line data itself. Company treat ACRA's Annual Return and IRAS Form C-S as the same process because they arrive at roughly the same time frame during the year and ignore the one which they were less distracted.
AIS employment income lodgement date (1 March of every year on prior year's income) also surprises entities because they are beyond the typical corporation tax filing cycles and could be less prioritized until IRAS chasing notices appear.
What to check before the next filing cycle, not after
A few questions are worth working through now, particularly for a business approaching GST registration or an InvoiceNow implementation date:
Is GST tax code mapping in the accounting system actually correct at the transaction level, or does it get "cleaned up" manually before each return?
Do they have the actual InvoiceNow target implementation date and are they under the impression they have until then?
Can someone be appointed as the ultimate responsible party for filing and submitting to IRAS, as distinct from someone in charge of ACRA's secretarial duties, so that one does not accidentally fall under the other?
For a group, is the filing status for each UEN handled separately rather than grouped?
If a tax agent is used, does a director have to check each filing, because liability does not get shared with a tax agent?
Where an ERP or localisation partner fits, and where it doesn't
This is where things stop being incidental to A Singapore ERP localisation, eg, Odoo Singapore, such as Serpentcs's solution Singapore package becomes relevant. Producing accurate IRAS and GST reporting in the accounting system from the outset, built using Singapore compliantchartof accounts and tax rules, also reduces a certain level of manual reconciliations that results in the coding errors to begin with. In the run-up to a mandatory roll out of InvoiceNow, for any ERP or Accounting System, be it Odoo or otherwise, the more pertinient question becomes can that platform properly map the GST tax codes to the PINT-SG data structure that will form a key input on InvoiceNow, because it should really be done properly once and just maintained, instead of being re done each quarter.
Having said that, not all businesses in Singapore require an ERP upgrade.
An SME that is simple and only does relatively few invoices might be happy to make do with a tailored accounting system, supplemented with a decent accounting agent plus a director that is actively checking the submissions, rather than an entire ERP system. Those who invoice a higher volume of sales or operate across more companies will most likely see stronger case for adopting ERP-centric approach, including those whose own tax code structures in accounting may not be as perfect as before. Regardless, who provided you with the software module or who is doing the work at the end of day is far less important, compared with whether somebody have properly tested that InvoiceNow mapping and actually works, before reliance is placed on it for a submission.
The point of all this
The IRAS aspect of compliance, which was in the past a company doing the math on the right form in the right format at the right deadline in retrospect, now is becoming an element of transaction completeness itself – something IRAS does see when the invoice is issued. Now, this doesn’t necessarily demand every business rethink and update their invoicing systems tomorrow. It suggests that the option of regarding IRAS compliance as a purely quarter-based accounting function, rather than intrinsically woven into business operations such as invoicing and bookkeeping, simply becomes increasingly costly with each completed invoice</b> </b> phase of the InvoiceNow program.
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FAQ
IRAS and ACRA handle different compliance responsibilities in Singapore. IRAS oversees corporate income tax, GST, and withholding tax, while ACRA manages company incorporation, annual returns, and annual AGMs. These obligations have separate deadlines and penalties, so being compliant with ACRA does not automatically mean a business is compliant with IRAS.
GST InvoiceNow requires GST-registered businesses to send invoice data to IRAS in a structured format based on PINT-SG and the Peppol framework through an accredited Access Point service provider. The requirement is being introduced in stages. New GST registrants have been brought into the requirement from 1 April 2026, while existing GST-registered businesses will be onboarded progressively from April 2028 to April 2031.
Missing an IRAS corporate tax filing deadline can lead to compliance issues and penalties. The blog highlights that companies must submit ECI within 3 months after the financial year end and the final corporate tax return (Form C-S, C-S Lite, or C) by 30 November of the following calendar year. Directors remain responsible for ensuring these obligations are completed, even when a tax agent is engaged.
Yes. The blog explains that the corporate tax obligations apply to Singapore-registered companies regardless of whether they are profitable or not. Companies still have fixed annual obligations, including ECI and the relevant final corporate tax return. Therefore, making a loss or having no activity does not automatically remove the company's filing responsibilities.
Yes. Engaging a tax agent does not transfer the director's ultimate responsibility. The blog specifically notes that directors retain personal responsibility for timely IRAS submissions, even when a tax agent handles the work. Directors should therefore ensure that the required filings are completed and submitted on time.
A business is required to register for GST when its annual taxable turnover exceeds S$1 million on a rolling 12-month basis. Once registered, the business generally collects 9% GST on qualifying sales and declares the GST collected against the GST paid when filing its GST returns.
The blog explains that existing GST-registered businesses are being onboarded to InvoiceNow in stages between April 2028 and April 2031. The specific implementation date depends on the applicable rollout schedule for the business. Companies should identify their target implementation date rather than simply assuming they have more time before the requirement applies.
The blog states that failing to file a GST return automatically incurs a penalty, while late payment of GST adds a surcharge that rises at 5% per annum. This makes timely GST filing and payment an important part of ongoing IRAS compliance.
