The operating model
A GST-registered business charges GST on standard-rated supplies, recovers GST paid on eligible purchases, and reports the net amount to IRAS, usually quarterly on Form F5. Output tax is collected on behalf of IRAS; input tax is recovered from IRAS; the net is payable or refundable.
- Standard-rated supplies: 9% GST, collected on behalf of IRAS.
- Zero-rated supplies: 0% GST, but still taxable, so input tax can usually be recovered.
- Exempt supplies: no GST charged, and related input tax is generally not recoverable.
- Out-of-scope supplies: outside the GST system, treated separately.
- Records normally need to be retained for 5 years from the relevant date.
When registration kicks in
A business must register for GST when its annual taxable turnover exceeds SGD 1 million. The test is forward-looking as well as retrospective: a business that expects to cross the threshold is expected to register within the prescribed window. Voluntary registration below the threshold is also possible and is common for SMEs that deal mostly with GST-registered customers or want to recover input tax on early setup costs.
- Compulsory registration when past or projected turnover exceeds SGD 1M.
- Voluntary registration available below the threshold, with conditions.
- Registration can be done online via myTax Portal using CorpPass or Singpass.
- Effective date of registration determines when GST can be charged and recovered.
Output tax: what you charge and what you can issue
Output tax is the GST you collect on taxable supplies. To support that collection, a GST-registered business must issue a tax invoice within the prescribed window from the time of supply, and the invoice must carry the information IRAS requires. A simplified tax invoice is allowed for retail receipts under SGD 1,000, but most B2B transactions need a full tax invoice.
- Standard tax invoice for B2B sales at or above the simplified-invoice threshold of SGD 1,000.
- Simplified tax invoice allowed for lower-value retail receipts under SGD 1,000.
- Credit notes and debit notes follow their own format and timing rules.
- The accounting period in which a transaction belongs depends on the time-of-supply rules and is checked against the relevant invoice, payment, delivery, or service-completion facts.
Input tax: recovery needs evidence
Input tax recovery depends on GST registration, business purpose, valid tax invoices, attribution to taxable supplies, and whether the expense is blocked under GST regulations. Common blocked inputs include club subscription fees, private motor car expenses, and family benefits. Mixed taxable and exempt supplies can require partial exemption apportionment, which is one of the more common F5 review failures for SMEs.
- Recovery is generally allowed for goods and services used to make taxable supplies.
- Blocked input tax cannot be recovered, even with a valid tax invoice.
- Partial exemption applies when supplies are mixed, with apportionment per the GST rules.
- A reverse-charge mechanism applies for certain imported services.
How the F5 fits into the picture
Form F5 is the GST return most Singapore SMEs file, usually quarterly. The F5 reports output tax collected, input tax recovered, and the net GST payable or refundable. For a Singapore SME, the F5 should not be a quarter-end reconstruction; it should be a review of already-coded evidence with a clear trail back to the source. The IRAS F5 guide covers the review pack and the workflow around that return.
- Quarterly filing is the default for most GST-registered businesses.
- Monthly and non-standard cycles are also possible, with conditions.
- Corrections after filing go through Form F7, not by editing the F5.
- Late or wrong filing carries penalties; review before you sign.
How Accountant Included fits
Accountant Included is being built around the Singapore GST operating model. The agent preserves source documents, drafts GST coding at transaction level, surfaces low-confidence or blocked-input cases for review, and assembles the F5 review pack from already-coded evidence. The reasoning log records the rule cited, the alternatives considered, and the confidence behind each draft. The review queue keeps the human in charge of sign-off; the audit trail preserves what was approved and why.
- Transaction-level GST drafting with the rule cited.
- Blocked-input and low-confidence cases surface before posting.
- F5 review pack assembled from coded transactions and source evidence.
- Reasoning log and audit trail correlated with each posted entry.