GST F5 Quarter-End Filing: A Singapore SME Checklist for the June 2026 Quarter

If your business is on a quarterly GST cycle, your June 2026 accounting period closes on 30 June and your GST F5 return must be filed and paid by 31 July 2026. The fastest way for a lean Singapore SME team to hit that deadline without errors is to start reconciling now: match your output tax to your sales records, confirm your input tax claims are properly supported, and — for the first time this year — cross-check the e-invoices flowing through InvoiceNow against your accounting ledger. This checklist breaks that work into the order you should tackle it, so the actual filing on myTax Portal takes minutes rather than days.

What exactly is due at the June 2026 quarter-end?

The GST F5 is your quarterly summary return. It reports your total standard-rated, zero-rated and exempt supplies, the output tax you collected at the prevailing 9% rate, and the input tax you are entitled to claim back on business purchases. The net figure is either payable to IRAS or refundable to you.

For the accounting period 1 April to 30 June 2026, the submission window opens on 1 July and closes on 31 July. A few non-negotiables worth flagging early:

• File even if it is a nil return. No activity in the quarter does not excuse you from submitting — a late or missing F5 attracts a $200 penalty for each month it remains outstanding, up to $10,000 per return.
• GIRO collections happen mid-August. If you pay by GIRO, the deduction is taken on the 15th of the month after the due date, so cash-flow planning matters for businesses in a net-payable position.
• Your figures must reconcile to source records. IRAS expects the F5 boxes to be traceable to your invoices, ledgers and bank statements. This is where most last-minute scrambles happen.

How do I reconcile sales and output tax before filing?

Start with output tax because it is the figure IRAS scrutinises most. Pull your sales report for the full quarter and reconcile it against three things: your invoicing system, your bank deposits, and any point-of-sale or e-commerce platform takings.

For SMEs that ran a high-volume sale period — a mid-year promotion or a 6.6 or 7.7-style event — pay particular attention to credit notes, returns and refunds. Every refund issued reduces your output tax, but only if it is properly documented with a credit note that references the original tax invoice. Miss these and you will overstate your GST payable and effectively pay tax on revenue you returned to customers. Build a simple reconciliation line: gross sales, less returns and credit notes, equals net standard-rated supplies. That net figure feeds Box 1.

Also separate your zero-rated exports and exempt supplies clearly. Misclassifying a local sale as a zero-rated export is one of the most common errors flagged in IRAS reviews.

What does InvoiceNow change for this quarter's reconciliation?

This is the new wrinkle for 2026. With the phased GST InvoiceNow requirement now in effect for newly registered businesses, a growing share of SMEs are transmitting invoice data to IRAS directly through the InvoiceNow network as e-invoices are issued and received. For many, the June quarter is the first full period where that data has been flowing.

The risk is a quiet mismatch: the e-invoice data IRAS receives in near real-time does not tie back to the figures in your F5. To avoid that, add an InvoiceNow reconciliation step before you file:

• Export the list of e-invoices transmitted and received through your InvoiceNow-enabled solution for 1 April to 30 June.
• Match the transmitted sales invoices to your output tax workings, and the received supplier invoices to your input tax claims.
• Investigate any invoice that exists in your accounting system but was not transmitted — or vice versa. Duplicates, failed transmissions and invoices issued outside the network are the usual culprits.

Treat this quarter as a calibration exercise. Getting the two data sets to agree now means future quarters reconcile almost automatically.

How do I make sure my input tax claims will survive an audit?

Input tax is where refunds are won and lost. You can only claim GST on purchases that are for business use, supported by a valid tax invoice (or simplified tax invoice for amounts up to $1,000), and that fall within the allowable categories.

Run through these before claiming:

• Disallowed expenses. GST on private cars, club subscriptions, medical expenses and most staff benefits cannot be claimed. Strip these out.
• Valid supporting documents. Every claim needs a tax invoice showing the supplier's GST registration number. No document, no claim.
• Imports. If you imported goods, your input tax is based on the import permit, not a supplier invoice — make sure these are captured.

A clean digital filing system pays for itself here. SMEs that store tax invoices against each ledger entry can reconcile input tax in an afternoon; those relying on a shoebox of receipts lose days and risk under-claiming.

What is the smartest way to file and avoid penalties?

Once your output tax, input tax and InvoiceNow reconciliations agree, filing itself is straightforward. Log in to myTax Portal with your Corppass, complete the F5 boxes from your reconciliation working, and submit. Keep your reconciliation file — the workings, the reports and the InvoiceNow export — for at least five years in case of review.

Two habits separate the SMEs that file calmly from those that panic on 30 July. First, close your books weekly rather than scrambling at quarter-end, so reconciliation is a review rather than a reconstruction. Second, automate the data flow between your invoicing, accounting and InvoiceNow tools so figures move without manual re-keying. For lean teams without a full finance function, this is exactly the kind of recurring compliance work that a managed-service arrangement can take off your plate entirely — turning a quarterly fire-drill into a background process.

Frequently asked questions

When is the GST F5 due for the June 2026 quarter?
For the accounting period 1 April to 30 June 2026, your F5 return must be filed and any GST paid by 31 July 2026. If you pay by GIRO, the deduction is taken on 15 August.

Do I still need to file if my business had no transactions this quarter?
Yes. A nil return is still mandatory. Failing to file on time attracts a $200 penalty for each completed month the return is late, capped at $10,000 per return.

What happens if my InvoiceNow data does not match my F5 figures?
A mismatch will not block your submission, but it raises your audit risk and may prompt IRAS queries. Reconcile the e-invoice export against your accounting ledger before filing, and correct any failed transmissions or duplicates so the two data sets agree.