A deposit is a first part payment of the agreed price, paid when the customer accepts the quote and before any work starts. It is not an extra charge: it comes off the final bill. On a trade job it usually does two things. It pays for materials you have to buy or order before you can start, and it shows the customer is committed, so you can book them in and turn other work away. It is normally stated as a percentage of the total and as a dollar figure, with the point at which it is due.
On jobs that count as domestic or residential building work, several states cap how large the deposit can be, and some say it cannot be taken until any required home warranty insurance is in place. The caps and the threshold for what counts as building work differ from state to state and change from time to time. Check with NSW Fair Trading, Consumer Affairs Victoria, the QBCC or your own state or territory's equivalent before you settle on a figure.
In practice
A metal fabricator quotes $4,000 for a pair of driveway gates built in the workshop, galvanised and powder coated. The steel and the galvanising have to be paid for in the first week, long before the gates are hung. So the quote asks for 25 per cent, $1,000, on acceptance, and the balance of $3,000 on installation. The note also says the steel is ordered once the deposit arrives, which makes the start date depend on the payment rather than on a promise that it is coming. Where a job like this counts as domestic building work in your state, the state's cap sets the figure instead of 25 per cent.
Two habits keep deposits clean. Ask for one only when there is a real cost in front of you, so it reads as fair rather than as a test. And state in the quote what happens to the deposit if the customer cancels after you have ordered made-to-measure materials, because that is the moment it gets argued about.
In Quote Desk
Quote Desk does not take deposits or any other money. Write the deposit, its due date and the payment method in the note, which the customer reads before pressing Accept this quote, and collect it the way you do now. The help article on what the quote builder does not do covers it.