The one-line answer: five items added together
Cash the buyer needs = price + ad valorem stamp duty (AVD) + buyer's agency commission + legal fee + miscellaneous costs. The mortgage portion is not cash, it is borrowing.
On a HK$6m flat with 1% commission on each side, a HK$8,000 legal fee and HK$5,000 of miscellaneous costs: HK$6,000,000 + HK$135,000 AVD + HK$60,000 buyer's commission + HK$8,000 + HK$5,000 = HK$6,208,000. There is no need to memorise this; enter the four numbers into the calculator and confirm.
Present it to a client as a single line plus a screenshot of the calculator result. What the client wants to know is not how many cost lines exist, but the size of the cheque they have to write.
Which figures are variables, and which are conventions
Three are variables: the commission rate, the legal fee and miscellaneous costs. The commission rate is negotiated between the parties and the agency, the legal fee depends on the firm and the property, and miscellaneous costs cover searches, deed documents and sundry disbursements.
Two are conventions: in the secondary market, 1% from each side is a market convention within a negotiable range, not a fixed statutory or regulatory rate. Commission structures for new launches change frequently and vary widely between developers and phases, so this article shows the arithmetic without publishing a standard rate.
The calculator exposes these as configurable inputs, with 1% per side, HK$8,000 and HK$5,000 as starting points, so you can enter the figures actually agreed rather than accept the defaults.
The initial deposit is a different question
The deposit paid when the provisional agreement is signed is a payment within the transaction, and it counts towards the price, so it does not add to the total cash requirement. What raises a buyer's cash requirement is the four cost lines beyond the price.
When explaining this, keep two timelines separate: when the deposit and down payment fall due, and how much the duties and fees amount to. Merging them leads clients to think the duty is smaller because a deposit has already been paid.
Why 1% per side must be labelled a convention
Commission rates are market practice and move with conditions and agency policy. In the primary market, am730 reported in 2024 that the four largest agencies issued internal notices from 2024-01-01 requiring a minimum 2% net commission on new launches, while Sing Tao reported even more complex competition on primary commission in a quiet market. Those figures come from media summaries of market conditions, not from any regulator.
That is why this article and the calculator never state a standard industry rate. Describing a rate as agreed rather than prescribed avoids disputes later.
Two inputs that move the result most
The first is property type. Residential and non-residential property follow different scales, and non-residential above HK$21,739,120 is charged at 4.25% rather than 6.5%.
The second is the buyer and seller commission rates. The calculator returns both the buyer's cash requirement and the cash across the whole deal. The first is the client's answer; the second is what you and a co-broke partner work from.