GST on aircon work in Singapore: how to read a quote
One quote carries a GST line, the other does not, and the cheaper one starts to look suspect. Neither answer says much about the operator. What changes the comparison is whether each quote states which basis it used.
By Team Snowflake | Updated 9 Aug 2026
Why a quote with no GST line is ordinary
Singapore ties GST registration to size, not to standing. The First Schedule to the Goods and Services Tax Act makes a business liable to register once the total value of its taxable supplies in a calendar year passes one million dollars. The same duty arrives earlier if there are reasonable grounds to believe the figure will be passed in the twelve months then beginning. Both tests measure sales volume. Neither of them asks anything about the quality of the work being sold.
Below that line, registration becomes a choice. The Act sets out voluntary registration separately, and it lets a business that is not liable to register ask to be registered anyway, with the decision resting on the Comptroller. So two honest operators can produce two different quotes. One sits below the threshold and quotes with no tax on it. The other sits above the threshold and quotes with the tax already inside the number.
The tax also cannot be charged by just anyone. The Act makes it an offence to collect, or attempt to collect, an amount as tax where the collector has no entitlement to do so. The penalty attached runs to several times the sum collected. A small firm quoting with no tax line is following that rule, and reading the absence as evasion gets the arrangement exactly backwards.
None of this makes the presence of a GST line a mark of quality either. Crossing the threshold means a business sold more in a calendar year, which usually means more vans, more technicians, or more years in operation. Those things track scale. They say nothing about who will diagnose the fault correctly. A homeowner who picks on the tax line alone has swapped one poor proxy for another.
Crossing the threshold is a date, not a permanent status
Liability attaches at a moment, and it can also fall away. The backward-looking test is assessed at the end of a calendar year. The forward-looking one bites at any time the next twelve months are expected to pass the figure. The Act then allows relief where the Comptroller is satisfied the coming year will stay under it, so a business that crossed once is not locked in for good.
That has a practical edge for a returning customer. An operator used for years with no tax on the invoice may issue the next one with the tax added, and the change is a threshold event, not a quiet price rise. Asking when the registration took effect settles it in one message, and the answer is a date the business can state plainly.
What the tax is charged on, and at what rate
The rate has been 9% since 1 January 2024. Section 16 of the Act carries the full ladder behind it: 4% in 2003, 5% from 2004, then 7% for most of the two decades that followed. An 8% year ran through 2023, and 9% has applied from that date with no end attached. Older material still quoting 7% or 8% is the usual reason two sources appear to disagree. Check the date on anything that states a rate before using it.
Parts and labour sit at the same rate. Section 16 charges the tax on the supply of goods or services, using one figure for both, so an invoice split into a compressor line and a labour line gets no different treatment from one showing a single total. A supply-and-install job is charged the same way as a visit that fits nothing at all. The split on the page is a matter of transparency, and it changes nothing about the tax.
Aircon work also falls outside the exempt categories. Those categories are narrow. They cover financial services, the sale and lease of residential property, and investment precious metals. Servicing, repairing or installing a unit is a supply of services made in Singapore, so it sits in the ordinary standard-rated group. An HDB flat, a condo unit and a shop are treated alike. The property type changes the access and the scope, not the tax.
One consequence of a flat rate is worth carrying into any comparison. The same percentage applies to parts, labour and installation alike, so the tax cannot explain why one quote is higher than another. It scales both quotes by the same proportion and leaves the gap between them intact. If two numbers sit far apart, the reason is in the scope.
Rounding explains the last dollar or two, and nothing more. IRAS allows a business to work out the tax line by line and add up the results, or to work it out once on the total before tax. Both methods are acceptable as long as one of them is used consistently. Two quotes covering identical work can therefore land a few cents apart on the tax line with neither being wrong.
Inclusive, before GST, and the comparison that goes wrong
A registered business is meant to quote the tax-inclusive figure already. IRAS puts the rule plainly in its general guide. Prices displayed, advertised, published or quoted to the public must show the price with the tax in it. The rule covers written and spoken quotes alike. The guide's own examples treat a bare number followed by plus GST as a display format that fails. Every acceptable version leads with the total the customer pays.
Where both figures appear together, the inclusive one has to be at least as prominent as the exclusive one. That detail earns its keep when a quote leads with a large round number and tucks the real total into smaller type underneath. Breaching the price display rule is an offence that carries a fine. Even so, a quote built the wrong way round is worth one clarifying question and no more. It is a formatting problem, not a character reference.
The failure mode is a comparison run across two different bases. An inclusive quote and an exclusive quote for identical work look 9% apart when the work behind them is the same, and the whole gap is an artefact of how the two pages were written. Put both onto one basis before anything else. Multiply an exclusive figure by 1.09, or take the tax fraction, 9 over 109, out of an inclusive figure to recover the number before tax.
A number given over the phone deserves the same treatment. The display rule covers spoken quotations, so a figure quoted on a call by a registered business should already carry the tax inside it. Getting the same number in writing is still the safer habit. A spoken figure is the one nobody can check afterwards. Each side also tends to remember it on a different basis, which is how an argument about scope becomes an argument about arithmetic.
| What the quote says | What you actually pay | What to do before comparing |
|---|---|---|
| What the quote saysTotal, marked inclusive of GST | What you actually payThe number as printed | What to do before comparingCompare it directly against other inclusive totals |
| What the quote saysTotal, marked before GST | What you actually payThe number plus 9% | What to do before comparingMultiply by 1.09, then compare |
| What the quote saysNo mention either way, operator is registered | What you actually payShould already be the inclusive total | What to do before comparingConfirm in writing before treating it as final |
| What the quote saysNo mention either way, operator is not registered | What you actually payThe number as printed | What to do before comparingCompare it directly, with no adjustment |
When the number gets negotiated
Bargaining does not move the quote off an inclusive basis. IRAS addresses the case directly: where a retail price is open to negotiation, the price quoted should still be the tax-inclusive one, and the business accounts for the tax as a fraction of whatever the customer finally pays. The tax follows the settled figure down.
So a discount agreed on site reduces the tax with it, and no separate adjustment is owed at the end. A revised total that somehow lands above the discount agreed is worth querying before payment. The arithmetic on a negotiated job is the same arithmetic as on a quoted one, applied to a smaller number.
What the paperwork looks like on each side
A homeowner rarely receives a tax invoice, and that is the system working as designed. The tax invoice exists so a GST-registered customer can support an input tax claim, which makes it a business-to-business document. IRAS says it need not be issued to a customer who is not registered. For a household, a registered operator may issue a receipt in its place, and the receipt is where the tell sits.
The receipt has a set shape. IRAS requires it to show the business name and GST registration number, the date, the total payable including the tax, and a line saying that the price payable includes GST. Those two items, the number and that line, are the tell. A homeowner who knows to look for them has the answer without asking anybody anything.
A business that is not registered must not issue a tax invoice at all. The same IRAS guide lists that among the cases where a tax invoice is barred. It explains why paperwork from a smaller operator can look thinner on the page. An ordinary invoice with no tax line and no registration number is the right output below the threshold. Asking for a tax invoice there is asking for a document the business cannot lawfully give.
The number on a receipt can be checked against the register. IRAS runs a GST Registered Business Search as a public service, and a number either matches a registered business or it does not. Use it to settle a quote that reads ambiguously. Running it on everyone who walks into the flat turns a two-minute clarification into a habit of suspicion, and it will never surface the thing that actually matters about a contractor.
| Situation | What the paperwork shows | What it tells you |
|---|---|---|
| SituationOperator is registered | What the paperwork showsRegistration number, plus a line stating the price includes GST | What it tells youThe quoted figure should already contain the tax |
| SituationOperator is not registered | What the paperwork showsNo tax line, no registration number, and no tax invoice | What it tells youThe quoted figure is the whole figure |
| SituationQuote and receipt both silent | What the paperwork showsNothing either way | What it tells youAsk once, in writing, before approving the work |
When the quote says neither, and what to ask
One question closes the gap: is this figure inclusive of GST. Put it in writing and keep the reply next to the quote. A registered business should confirm the total already carries the tax. A business below the threshold should confirm that none applies. Either reply is a complete answer. A quote that cannot produce one in a sentence has a bookkeeping problem worth knowing about before the work starts.
Two replies deserve a closer read. Absorbing the tax and having no tax to charge are different claims. IRAS treats the second as misleading where a registered business is in fact discounting by the tax amount, since a tax element still sits inside everything such a business supplies. An absorbed tax is a discount under another name. Discounts get withdrawn, and the total that returns later is the one that was always there.
None of this is a verdict on who to hire. The basis a quote was written on tells you how to read the number in front of you. What a tax basis cannot tell you is whether the diagnosis behind the number holds up, and that is the half where the money goes. A quote settled on tax and wrong on scope still ends with the wrong work being done, and every page of it will have been correctly taxed.
So treat the tax question as the quick one. Confirm the basis in a message. Put the competing quotes onto that same basis. Then turn to what each one claims was found, and what it proposes to do about it. Sending a quote alongside a description of the symptom lets both halves be read together, and that is where a second opinion earns its place.
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