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A Comprehensive guide to the Inland Revenue Authority of Singapore (IRAS)

A Business Guide to IRAS: What You Must File, and When

  • Modified On: October 12, 2026

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Running a company in Singapore, or about to set one up?

Singapore’s tax system is one of the most competitive in the world, but only if you stay on the right side of the Inland Revenue Authority of Singapore (IRAS). Late filings, missed registrations and incorrect submissions can lead to penalties and unwanted scrutiny.

This guide explains what IRAS does, which taxes it administers, the filing obligations every business should know, and where companies commonly go wrong.

Quick Facts

Topic What to know
Who is IRAS? Singapore's national tax authority, a statutory board under the Ministry of Finance.
Revenue role Collects taxes that make up roughly 70% of the government's operating revenue.
Main taxes Corporate income tax, individual income tax, GST, property tax and stamp duty.
Not taxed Capital gains, inheritance and (generally) dividends received.
How you deal with IRAS Online, through the myTax Portal, using Singpass (individuals) or CorpPass (businesses).

Taxes IRAS administers

IRAS administers the following taxes. Some other duties, such as customs and excise duties, are handled by other agencies.

  • Corporate income tax: charged on company profits arising in or received in Singapore.
  • Individual income tax: charged on income of residents and certain non-residents, including directors and employees.
  • Goods and Services Tax (GST): a consumption tax on most goods and services, including imports.
  • Property tax: charged to property owners based on the annual value of the property.
  • Stamp duty: charged on certain documents, including property transactions and share transfers.
Singapore does not tax capital gains or inheritance, and most dividends are not taxed in the hands of shareholders.

What IRAS expects from your business

Obligation What it involves Key timing
Corporate tax rate Singapore's headline corporate tax rate is 17%. Start-up and partial tax exemptions can reduce the effective rate for qualifying companies. Applies to each Year of Assessment
Estimated Chargeable Income (ECI) A first estimate of your taxable income for the year, filed with IRAS. Generally within 3 months of financial year-end (some companies qualify for a waiver)
Annual corporate tax return Form C-S, Form C-S (Lite) or Form C, depending on company size and complexity. Generally by 30 November each year
GST registration Mandatory once taxable turnover exceeds the registration threshold. Voluntary registration is also possible. Within the period IRAS specifies once the threshold is crossed
GST returns Periodic returns declaring GST collected and paid. Usually quarterly, due one month after period-end
Record keeping Retain accounting and tax records. At least 5 years
Missing these dates can lead to late-filing penalties, composition fines, or estimated assessments raised by IRAS. For foreign-owned companies and new start-ups, the first year of compliance is when mistakes are most likely.

Common mistakes companies make with IRAS

  1. Missing ECI or filing it late because the financial year-end falls early in the year or the team assumes the accountant has done it.
  2. Registering for GST too late after turnover has already crossed the threshold.
  3. Claiming expenses that aren’t deductible or lacking documents to support a claim during a review.
  4. Overlooking start-up and partial exemptions and paying more tax than necessary.
  5. Mismatch between accounts and tax filings when bookkeeping and tax are handled by different providers.
  6. Weak record keeping, which becomes a problem when IRAS asks for supporting documents.

How to deal with IRAS online

To check your tax status, file returns or view notices, log in to the myTax Portal. Individuals use their Singpass. Companies and businesses use CorpPass, which must be set up with authorised users assigned by the entity.

Many accounting packages can also submit data to IRAS directly, but only if the software meets IRAS technical requirements and appears on its approved list.

Contacting IRAS

For general questions, you can contact IRAS through its website, helpline, email or a visit to its office. The helpline is open on weekdays; check the IRAS website for current hours and numbers. For business registration questions, ACRA and Enterprise Singapore also have helplines.

When it makes sense to bring in an expert: IRAS can explain the rules, but it can’t prepare your filings, plan your tax position or represent your company’s interests. If you’re handling more than basic compliance, such as cross-border income, group structures, or an IRAS query letter, it’s worth having a specialist on your side.

A short history of IRAS

IRAS traces its roots to the Singapore Income Tax Department, set up in 1947 to administer the Income Tax Ordinance. In 1960, revenue collection that had been spread across several agencies was brought together as the Inland Revenue Department. In 1992, IRAS was established by legislation as a statutory board under the Ministry of Finance, taking over the department’s functions.

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Frequently Asked Questions

Do I need to register for GST in Singapore?
GST registration is mandatory once your taxable turnover goes over the threshold set by IRAS, currently S$1 million (verify). Below that, you can still register voluntarily, which can make sense if you have significant input GST to claim. Our team can assess which route suits your business.
When is the corporate tax filing deadline?
Most companies must file their annual tax return (Form C-S or Form C) by 30 November each year, with ECI due earlier, generally within three months of financial year-end. Deadlines can vary, so confirm your own dates (verify).
What happens if I file late or don't file?
IRAS may impose penalties, issue fines, or raise an estimated Notice of Assessment based on available information. Repeated or serious non-compliance can lead to prosecution. Filing late is almost always more expensive than filing on time.
Can a foreign-owned company claim tax exemptions in Singapore?
Yes, subject to eligibility. Qualifying new companies can claim the start-up tax exemption in their first years, and all companies may benefit from partial exemption on part of their chargeable income. Eligibility depends on shareholding and activity, so it should be checked case by case.
Can an accounting firm file with IRAS on my behalf?
Yes. Authorised tax agents and corporate service providers can prepare and submit filings for your company once appropriately authorised. This is a common option for companies with directors based overseas.
Do I still need to file if my company has no revenue?
Yes. Dormant or loss-making companies usually still have filing obligations unless IRAS has granted a waiver. Check before assuming you are exempt.

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Author Bio:
Shivani
Shivani Bhakar works with international businesses on cross-border expansion, corporate structuring, regulatory compliance, and reporting requirements across different jurisdictions. She supports companies in understanding regulatory expectations and establishing practical approaches for market entry and ongoing business operations. With a strong focus on compliance and governance, she helps business leaders make well-informed decisions as they expand across regional and international markets.

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