Goods and Services Tax (GST) is a central component of Singapore’s tax system, affecting nearly every business transaction. If you own or manage a business in Singapore, especially as a small business owner, entrepreneur, or e-commerce seller, understanding how GST works is essential.
This guide explains input tax, output tax, and the critical compliance steps businesses must follow to meet their obligations with the Inland Revenue Authority of Singapore (IRAS).
What Is GST in Singapore?
GST is Singapore’s version of a value-added tax (VAT). It’s levied on the consumption of goods and services and administered by IRAS. GST is charged 9% (as of 1 January 2024) on most local supplies and imports. Businesses registered for GST collect this tax from their customers (output tax) and can reclaim GST paid on their purchases (input tax). The tax was originally introduced in 1994 and has since evolved to accommodate economic changes. GST is administered by the Inland Revenue Authority of Singapore (IRAS).
GST applies to most goods and services unless classified as exempt (like residential property and certain financial services) or zero-rated (such as exports and international services). Although consumers pay GST, businesses are responsible for collecting and remitting it.
Understanding Input Tax and Output Tax
To stay GST-compliant in Singapore, you need a clear grasp of two essential components: input tax and output tax. These form the basis of your GST calculations and filings; misunderstanding them can lead to overpayments or penalties.
What Is Output Tax?
Output tax refers to the GST charged by GST-registered businesses on the sale of taxable goods and services. It must be included on all tax invoices and collected at the point of sale. Businesses then report this amount to IRAS for quarterly GST filings.
For instance, if a GST-registered retailer sells electronics worth S$10,000, they charge the customer S$900 GST (9%). This S$900 is output tax and must be reported to IRAS.
GST Calculator
What Is Input Tax?
Input tax is the GST incurred by a business when it purchases goods or services for its operations. This includes raw materials, utilities, rental expenses, business software, and professional services. Unlike output tax, which is collected from customers, input tax is initially paid out of pocket and later reclaimed from IRAS, provided specific conditions are met.
Common Input Tax Examples:
- Office supplies
- Equipment and software
- Rental costs
- Professional services
To claim input tax:
- The business must be GST-registered.
- The expense must be business-related.
- A valid tax invoice or import permit must be available.
Claim Conditions
IRAS has established specific and enforceable rules to ensure input tax is only claimed under legitimate business circumstances. These conditions are designed to prevent abuse and over-claiming and ensure that businesses only recover GST when it’s directly related to taxable business operations.
- Payment to the supplier within 12 months: If you fail to pay the supplier within this time, the input tax must be reversed.
- Claim period: Input tax must be claimed in the correct GST return period, or within five years from the invoice date.
- Blocked claims: GST on certain expenses (e.g. cars for private use, club memberships, medical expenses) is not claimable.
- Partial exemption rules: If a business makes both taxable and exempt supplies, input tax must be apportioned accordingly.
Calculating and Reporting Net GST
Proper calculation and reporting of GST is one of the most critical compliance duties for GST-registered businesses in Singapore. To stay compliant, businesses need a clear understanding of determining their net GST position and how to file their returns accurately using IRAS’s systems.
Net GST = Output Tax – Input Tax
When filing a GST return, a business must determine the difference between the GST collected (output tax) and the GST paid on business expenses (input tax):
- Positive net GST: If output tax is higher than input tax, the business must pay the difference to IRAS.
- Negative net GST: If input tax exceeds output tax, the business is entitled to a GST refund.
Getting this calculation right each quarter is essential, as under-reporting can lead to penalties and over-reporting may delay refunds or cause cash flow issues.
IRAS GST Filing Requirements and Reporting Process
To remain compliant with Singapore’s Goods and Services Tax (GST) regulations, businesses must understand how GST filing works, including frequency and deadlines, as well as platform usage and submission protocols. Below is a breakdown of key GST filing requirements, as outlined by the Inland Revenue Authority of Singapore (IRAS), along with their connection to broader corporate tax obligations.
GST Filing Frequency and Deadlines
- Quarterly filing (default): Most businesses in Singapore are assigned a quarterly GST accounting cycle. Common cycles include Jan–Mar (due 30 Apr), Apr–Jun (due 31 Jul), and so forth.
- Monthly or special cycles: Businesses with high transaction volumes or specific operational needs may request monthly filing.
- Strict deadlines: GST returns and corresponding payments must be submitted within one month from the end of each accounting period. Missing these deadlines triggers late submission penalties and potential follow-up by IRAS.
It’s recommended to set internal reminders and plan, especially around public holidays or year-end busy periods.
Filing Platform: MyTax Portal
IRAS requires GST returns to be filed electronically via the MyTax Portal. The primary form used is Form F5, which summarises your business’s taxable supplies and GST obligations. The key boxes include:
- Box 1: Total value of standard-rated supplies (with output tax)
- Box 2: Total value of zero-rated supplies
- Box 3: Total value of exempt supplies
- Box 5: Input tax claimed
Even if your business has no sales or purchases in a given period, a nil return is still mandatory. Filing a nil return late incurs the same penalties as a full return.
Consider integrating your accounting system with IRAS’s portal or using InvoiceNow-compatible software to ease the administrative burden. These tools can streamline data entry and reduce manual errors in reporting.
Filing Corporate Taxes Alongside GST
While GST filing is a regular part of your accounting cycle, it’s only one piece of your broader compliance responsibilities. All Singapore-registered companies are also required to file corporate income tax annually with IRAS.
If you’re unsure about deadlines, exemptions, or the e-filing process, check out our complete guide to corporate tax filing compliance in Singapore. It outlines how to file Form C/C-S, estimate chargeable income, and avoid late penalties.
Invoicing and Record-Keeping Compliance
Invoicing and record-keeping are fundamental to GST compliance in Singapore. Failure to issue proper tax invoices or maintain required documentation can lead to penalties, input tax rejections, or even audit findings by IRAS. This section breaks down the key invoicing rules and record-keeping expectations for all GST-registered businesses.
Invoicing Standards
GST-registered businesses must issue tax invoices for all standard-rated taxable supplies made to other GST-registered parties. These invoices serve as the legal basis for input tax claims by your customers and must be issued within 30 days of the supply.
A valid tax invoice must include:
- The words “Tax Invoice”
- A unique invoice number
- The date of issue
- The name, address, and GST registration number of the supplier
- The name and address of the customer (if the amount exceeds S$1,000)
- A clear description of the goods or services supplied
- The quantity or period of supply
- The amount payable before GST
- The GST amount charged
- The total amount, including GST
A simplified tax invoice may be issued for smaller transactions (≤ S$1,000). These can omit the customer’s name and address and may show the total amount inclusive of GST or state that GST is included in the price.
You must also issue credit or debit notes to adjust any overcharges, returns, or pricing errors. These adjustments must be clearly linked to the original invoice to ensure correct reporting of GST.
Electronic Invoicing: InvoiceNow
Starting May 2025, all newly registered GST businesses in Singapore must adopt InvoiceNow as part of the digital compliance shift. InvoiceNow is an electronic invoicing network based on the international PEPPOL standard. It enables GST invoices to be sent directly between businesses’ accounting systems and reported to IRAS in near real-time.
Using InvoiceNow offers several benefits:
- Reduced manual data entry and errors
- Faster invoice processing and approval cycles
- Quicker GST refunds and clearer audit trails
Eventually, this requirement will expand to include existing registrants. IRAS encourages early adoption, and various government grants support implementation.
Record Keeping
Proper record keeping is both a legal and practical necessity for GST compliance. Businesses must retain all GST-related documents for at least five years from the end of the accounting period to which they relate.
These include:
- Tax invoices (issued and received)
- Simplified invoices
- Credit and debit notes
- Receipts
- Import and export permits
- Delivery orders and proof of shipment (for zero-rated exports)
- Contracts or agreements supporting taxable transactions
- Payment records such as bank statements and GIRO confirmations
- GST account ledger showing input and output tax calculations
Electronic storage is permitted, but records must be complete, legible, retrievable, and safeguarded against tampering. IRAS accepts digital copies provided they are accurate representations of the original documents.
Maintaining these records supports your ability to justify input tax claims and output tax charges during an audit or review. Using a cloud-based accounting system compatible with InvoiceNow can greatly simplify record-keeping and compliance workflows.
Best Practices for Compliance
Businesses that embed good GST habits into their workflows are far more likely to stay compliant and reduce audit risk.
- Use IRAS-approved accounting systems: These systems simplify compliance and ensure you capture required data fields correctly for GST filing.
- Set automated filing reminders: Schedule alerts before return deadlines to avoid penalties for late submissions.
- Train staff on invoice standards and GST rules: Everyone involved in finance or operations should understand how to handle GST-compliant invoicing.
- Regularly reconcile your GST ledger with return filings: Mistakes often arise from discrepancies between internal records and what’s submitted—perform quarterly checks.
- Adopt InvoiceNow early for future-proof compliance: Singapore is moving toward digital tax reporting. Onboarding early gives you a competitive edge in terms of compliance and efficiency.
- Subscribe to IRAS updates and review e-Tax guides annually: GST rules evolve. Keep your business informed about rate changes, procedural updates, and digitalisation requirements.
Practical Actions for Sustained GST Compliance
GST is a regulatory requirement critical to running a legitimate and scalable business in Singapore. As IRAS tightens digital compliance and updates filing expectations, proactive GST management becomes essential. Staying compliant means building systems that adapt to new rules and digital processes.
- Review your GST registration threshold regularly. Don’t wait until you’ve exceeded it.
- Standardise your invoicing and records. Keep them IRAS-compliant and easily retrievable.
- Use InvoiceNow-ready tools. Automate your GST workflows before they become mandatory.
- Watch for IRAS updates. Changes to export documentation and digital filing will affect your next return.
Explore IRAS’s official guides, or consult a qualified tax advisor to audit your current practices.
