GST F5 Filing Guide for Small Businesses in Singapore (2026)

If your business is GST-registered in Singapore, filing GST F5 is a task you face every quarter. For many small business owners, it's one of the more nerve-wracking parts of running a company — not because it's technically complex, but because the numbers have to be right. An incorrect GST return can trigger an audit, result in penalties, or leave money on the table that you're entitled to claim back.

This guide walks you through exactly what GST F5 is, how to prepare it correctly, the deadlines you can't miss in 2026, and the errors that trip up Singapore SMEs most often.

What Is GST F5?

GST F5 is Singapore's standard quarterly GST return form. It's the document you submit to IRAS (Inland Revenue Authority of Singapore) to report:

• The output tax you've collected from customers on your taxable sales
• The input tax you've paid on your business purchases and expenses
• The net GST you owe to IRAS — or the refund you're due

The "F5" distinguishes it from other GST forms like F7 (for correcting errors in past returns) and F8 (for the final return when you deregister). If you're a standard quarterly GST registrant, F5 is the form you'll be using four times a year.

Since 1 January 2024, the GST rate in Singapore is 9%. This applies to standard-rated supplies — most goods and services sold in Singapore. Zero-rated supplies (like international services and exported goods) are taxed at 0%, and exempt supplies (like financial services and residential property) don't attract GST at all.

Who Needs to File GST F5?

You must file GST F5 if your business is GST-registered with IRAS. GST registration is compulsory if your taxable turnover exceeds S$1 million in the past 12 months or you expect it to exceed that threshold in the next 12 months.

You can also register voluntarily if your turnover is below S$1 million — and there are good reasons to do so if you have significant input tax to recover, for example if you're buying equipment or materials with GST.

Once registered, you must file GST F5 every quarter — even if your business had no transactions in that period. A nil return is still a return, and failing to file is a compliance offence.

GST Accounting Basis: Invoice vs Payment

Before we dive into the numbers, one important distinction: most businesses in Singapore use the invoice basis (also called accrual basis) for GST accounting. This means you account for GST when an invoice is issued, not when cash is received. If you're on cash basis (permitted for businesses under S$1 million turnover), you account for GST when payment is received or made.

If you're unsure which basis you're on, check your GST registration letter from IRAS — it will specify.

GST F5 Filing Deadlines for 2026

GST F5 must be filed and payment made within one month after the end of each accounting period. For most standard quarterly filers, the deadlines in 2026 are:

• Q1 2026 (Jan–Mar): Due by 30 April 2026
• Q2 2026 (Apr–Jun): Due by 31 July 2026
• Q3 2026 (Jul–Sep): Due by 31 October 2026
• Q4 2026 (Oct–Dec): Due by 31 January 2027

Missing a filing deadline carries a penalty of up to S$10,000 plus 5% late payment penalties on any outstanding tax. If you're consistently late, IRAS may take enforcement action or issue a Demand Notice. Set calendar reminders well ahead of these dates — not the day before.

Understanding Output Tax and Input Tax

The two most important figures in your GST F5 return are output tax and input tax. Getting these right is the difference between a clean submission and one that invites scrutiny.

Output Tax: What You Collect

Output tax is the GST you charge on your taxable supplies to customers. For standard-rated supplies, this is 9% of the value of the supply. When you issue a tax invoice to a GST-registered customer, you collect this on behalf of IRAS — it's not your money to keep.

Your Box 1 (Total Value of Standard-Rated Supplies) should equal the total net value (excluding GST) of all standard-rated supplies you made during the period. Box 6 is the actual GST amount on those supplies.

Input Tax: What You Can Claim Back

Input tax is the GST you've paid on your business purchases and expenses — things like office supplies, equipment, professional services, and software. You can claim this back against your output tax liability, effectively reducing what you owe IRAS.

But not all input tax is claimable. You cannot claim input tax on:

• Private cars (S-plated vehicles)
• Club subscriptions and entertainment expenses where there is no business purpose
• Medical expenses unless they're for work injury compensation
• Purchases used to make exempt supplies

Box 5 is your total value of taxable purchases. Box 7 is the input tax you're claiming. Make sure every input tax claim is supported by a valid tax invoice in your business's name, showing the supplier's GST registration number.

Completing the GST F5 Form: Box by Box

The GST F5 form on myTax Portal has nine key boxes. Here's a plain-English breakdown:

• Box 1 — Total value of standard-rated supplies (9% GST applies)
• Box 2 — Total value of zero-rated supplies (0% GST — e.g. exports)
• Box 3 — Total value of exempt supplies (no GST — e.g. rent from residential property)
• Box 4 — Total value of out-of-scope supplies (not subject to GST)
• Box 5 — Total value of taxable purchases (what you bought with GST paid)
• Box 6 — Output tax due (9% of Box 1)
• Box 7 — Input tax claimed (GST paid on business purchases)
• Box 8 — GST payable or refundable (Box 6 minus Box 7)
• Box 9 — Total value of goods imported under Approved Trader schemes (if applicable)

If Box 8 is positive, you owe IRAS that amount. If it's negative, you're due a refund — IRAS will typically process this within 30 days for clean returns.

Common GST F5 Mistakes Singapore SMEs Make

IRAS audits aren't random — they're often triggered by patterns that flag returns as inconsistent or suspicious. Here are the most common errors that lead to scrutiny:

1. Claiming input tax without valid tax invoices

This is the most frequent error. Every input tax claim must be backed by a tax invoice showing the supplier's name, GST registration number, invoice number, the amount, and the GST charged. Receipts without GST registration numbers don't count. Bank statements alone don't count.

2. Mixing personal and business expenses

Sole proprietors and freelancers sometimes claim input tax on expenses that are partly personal — home internet, mobile phone, vehicle running costs. IRAS expects you to apportion these correctly. Claiming 100% input tax on a phone bill when 40% of usage is personal is incorrect.

3. Accounting for GST on the wrong period

If you use the invoice basis, you must account for GST in the period the invoice is dated, not when you receive payment. Getting this wrong leads to numbers that don't reconcile across periods and can appear as underreporting.

4. Missing zero-rated or exempt supplies in Boxes 2 and 3

If you make zero-rated supplies (e.g. export services to overseas clients) or exempt supplies (e.g. subletting residential space), these must be declared even though no GST is charged. Leaving Boxes 2 and 3 empty when they should have values can raise flags.

5. Late filing or non-filing

Submitting a nil return late is still a compliance failure. Even in a quiet quarter with no transactions, file on time. IRAS has automated systems that track late submissions.

Step-by-Step: Filing GST F5 on myTax Portal

Here's how to file GST F5 online through myTax Portal (mytax.iras.gov.sg):

1. Log in using your Singpass or Corppass credentials
2. Navigate to GST → File GST Return
3. Select the relevant accounting period
4. Fill in Boxes 1–9 based on your records
5. Review the summary and ensure Box 8 is correct
6. Submit — you'll receive an acknowledgement number
7. If tax is due, pay via PayNow (UEN reference) or GIRO before the deadline

If you discover an error after submission, don't panic — you can file a GST F7 (amendment return) to correct it. IRAS generally takes a more lenient view of voluntary corrections than errors discovered during an audit.

GST Record-Keeping Requirements

You must keep all records supporting your GST return for at least 5 years. This includes:

• Tax invoices issued to customers
• Tax invoices received from suppliers
• Import and export documentation
• Bank statements and payment records
• Business contracts relevant to GST treatment

IRAS can call up records from any of the past 5 years during an audit. Having everything organised and easily retrievable is not just about compliance — it's about being able to respond quickly and confidently if IRAS comes knocking.

Tools like app.kevinchia.sg automatically track your revenue and expenses throughout the quarter, so when it's time to file GST F5, you're pulling from organised, categorised records rather than hunting through email inboxes. Your P&L data maps directly to the values you need for each box.

Make GST Filing Less Painful

GST F5 doesn't have to be stressful if you stay organised throughout the quarter. The key is maintaining clean, categorised records of every taxable sale and purchase — not scrambling to reconstruct three months of transactions the week before the deadline.

Build a simple habit: once a week, review your transactions and make sure everything is categorised correctly. By the time the quarter ends, your F5 figures should be just a review away.

Frequently Asked Questions

What is the GST rate in Singapore in 2026?

9%, in effect since 1 January 2024. This applies to standard-rated supplies. Zero-rated supplies like exports are taxed at 0%, and exempt supplies like financial services and residential property don't attract GST at all.

When are GST F5 returns due in 2026?

One month after each quarter ends. For 2026: Q1 (Jan-Mar) is due 30 April 2026, Q2 (Apr-Jun) is due 31 July 2026, Q3 (Jul-Sep) is due 31 October 2026, and Q4 (Oct-Dec) is due 31 January 2027.

What happens if I file GST F5 late?

A penalty of up to S$10,000 plus 5% late payment penalties on any outstanding tax. If you're consistently late, IRAS may take enforcement action or issue a Demand Notice.

Can I claim input tax without a tax invoice?

No. Every input tax claim must be supported by a valid tax invoice showing the supplier's name, GST registration number, invoice number, the amount, and the GST charged. Receipts without a GST registration number don't count.

How long do I need to keep GST records?

At least 5 years. This includes tax invoices issued and received, import and export documentation, bank statements and payment records, and business contracts relevant to GST treatment.