GST GUIDE · UPDATED AUGUST 2026
GST F5 returns: the quarterly cycle, box by box
Once your business is GST-registered, the F5 becomes a permanent quarterly rhythm: return and payment due one month after each accounting period, nil activity or not. Most of the pain comes from three places — the boxes that exclude GST when owners expect them to include it, input tax claimed on blocked expenses, and errors fixed the expensive way when a concession would have covered them.
THE QUARTERLY CYCLE
Four returns a year, one month after each quarter.
Standard quarterly accounting periods. On GIRO, the deduction runs on the 15th of the month after the due date — the return must still be filed by the due date itself.
Accounting period
File & pay by
GIRO deduction
Jan – Mar
30 April
15 May
Apr – Jun
31 July
15 August
Jul – Sep
31 October
15 November
Oct – Dec
31 January
15 February
BOX BY BOX
The boxes that decide your GST position.
Everything is declared in Singapore dollars, at the current 9% rate. For a typical SME the return comes down to eight boxes.
Standard-rated supplies — excluding GST
Sell something for S$100 plus S$9 GST and Box 1 takes S$100; the S$9 goes in Box 6. Deposits, consignment sales and disposals of business assets belong here too — asset disposals are the line SMEs forget most.
Zero-rated, exempt, and the total
Exports and qualifying international services are zero-rated (keep the export documents), exempt supplies go in Box 3, and Box 4 totals all three. Box 4 matters beyond this return — it is the base for the error-correction concession and your InvoiceNow phase.
Taxable purchases and input tax — tracked separately
Box 5 is the value of taxable purchases; Box 7 is the input tax you can actually claim. IRAS warns against deriving Box 7 by multiplying Box 5 by 9% — disallowed expenses and partial claims mean the two must be tracked independently in the books.
Output tax and the net position
Box 6 is GST charged on your supplies; Box 8 nets it against Box 7 to give the amount payable to IRAS — or refundable to you. The form runs to Box 17, but Boxes 9 to 17 cover schemes, reverse charge and marketplace operators most SMEs never touch.
INPUT TAX
What Box 7 will not accept.
A valid tax invoice, addressed to you
Local claims need a tax invoice in the business's name — a simplified tax invoice is acceptable only where the supply is S$1,000 or less. Imports need the import permit showing you as importer.
Motor cars are blocked, however business the use
The cost and running expenses of motor cars are disallowed under Regulations 26 and 27 — petrol, parking, repairs and the car itself. This is the single most common wrongly-claimed category.
Club fees and most staff medical costs
Sports and recreation club subscription and transfer fees are blocked. Staff medical expenses are too, unless obligatory under the Work Injury Compensation Act or a collective agreement, or within the narrow work-related exceptions.
Business purpose, attributable to taxable supplies
Input tax must relate to making taxable supplies. Benefits for employees' family members and private or family expenses fail the business test outright.
FIXING ERRORS
Not every mistake needs a GST F7.
Small errors: adjust in the next F5
IRAS allows corrections in your next return if two tests both pass: the net GST amount in error across all affected periods is not more than S$3,000, and the errors in the other boxes are within 5% of that return's total supplies (Box 4) for each affected period. Older guides still say S$1,500 — the threshold is S$3,000.
Everything else: file a GST F7
Request the F7 on myTax Portal and e-file it within 14 days. It is the same form refiled in full with the corrected figures, and it supersedes the original return. Pre-registration claims in Box 12 can never use the next-F5 concession — they always need an F7.
Disclose early, pay less
Errors must be corrected within 5 years of the accounting period. Correct within a year of the original deadline under IRAS's voluntary disclosure conditions and penalties are reduced or waived; beyond a year, a 5% penalty attaches to the additional tax.
WHAT LATENESS COSTS
The penalties stack, and they compound.
Late filing: S$200, then S$200 a month
A S$200 penalty is imposed immediately after the due date, plus S$200 for every completed month outstanding, capped at S$10,000 per return. A nil return left unfiled collects the same penalty as one with tax due.
Late payment: 5%, then 2% a month
Unpaid GST attracts a 5% penalty, then an additional 2% per month once it is more than 60 days overdue, up to 50% of the outstanding tax. A failed GIRO deduction cancels the GIRO plan and makes the balance immediately due.
No return? IRAS estimates one
Non-filing brings an estimated Notice of Assessment with a 5% penalty on the estimated tax — and the estimate stands until the actual return is filed. Persistent default can end in a summons for the directors or partners personally.
Common questions.
When is the GST F5 due?
Both the return and payment are due one month after the end of the accounting period. On the standard quarterly cycle: 30 April, 31 July, 31 October and 31 January. IRAS treats one month as a reasonable deadline and generally does not grant extensions.
Do I need to file if there were no transactions?
Yes. A nil GST return must be filed even with no business activity in the period, and the same late-submission penalties apply if it is not.
When is GST deducted if I am on GIRO?
GIRO deductions happen on the 15th of the month after the payment due date — file the Jan–Mar return by 30 April and the deduction runs on 15 May. If the deduction fails, IRAS cancels the GIRO plan and the balance becomes due immediately.
I found an error in a filed return. Do I need a GST F7?
Not always. If the net GST in error across all affected periods is S$3,000 or less, and other-box errors are within 5% of each affected return's total supplies, you can adjust in your next F5. Outside those limits — or for Box 12 pre-registration claims — file a GST F7 within 5 years of the period.
What input tax can I not claim?
The blocked categories under Regulations 26 and 27 include motor car costs and running expenses, club subscription and transfer fees, most staff medical expenses and insurance, benefits for employees' families, and anything without a valid tax invoice or import permit. Claims must also relate to making taxable supplies.
How fast are GST refunds paid?
IRAS refunds tax credits automatically — within 3 months of receiving a quarterly return at the statutory limit, and it pays interest on credits not refunded within 30 days of arising, provided no returns or taxes are outstanding. Since 1 January 2026 refunds are paid via GIRO or PayNow only; IRAS no longer issues cheques.
Official sources
Deadlines, thresholds and penalty amounts are as published by IRAS, checked on 23 August 2026.
This guide provides general information, not tax advice. GST treatment depends on the nature of each supply and purchase, your accounting periods and any schemes the business is under, and IRAS rules and concessions can change.
WRITTEN BY
Jacqueline May
Principal Accountant · Chartered Accountant (Singapore), ISCA member
Jacqueline is a Chartered Accountant (Singapore) and ISCA member, and the Principal Accountant at Synergy Accounting, a Singapore practice established in 2013. She works on corporate tax, GST and ACRA compliance for small and medium businesses — the filings, deadlines and judgement calls most owners would rather hand over. These guides are written from what she sees in practice.