In South Australia a person can bid at an auction of residential land on someone else’s behalf. Before the agent may enter that person in the bidders register, the person must hand over a written authority signed by the buyer and show proof of identity for both of them. The state’s own buying guide puts it plainly: a buyer who would rather not bid can arrange for someone else to, and that person registers with their own details and identity and a document the buyer has signed.
General informationA summary of South Australia’s auction rules, not legal advice about any purchase. Consumer and Business Services (CBS) is where a problem with an agent goes, after the first steps SA.GOV.AU lists. A solicitor or conveyancer can advise on a particular purchase.
An agent under the Land Agents Act 1994 must be registered under that Act.
Before the auction: the bidders register
Land and Business (Sale and Conveyancing) Act 1994, section 24J
The seller’s agent, the one holding the sales agency agreement, keeps a written auction record, and part of it must be made before the auction begins: a bidders register of everyone who intends to bid.
The order matters. Nobody’s details go into that register until their identity has been established. Where the intending bidder will bid for someone else, two more things come first: that person’s authority to act, and proof of the other person’s identity, both obtained as the Regulations require.
Each person registered is also handed a written guide to buying residential land at auction, in a form the Commissioner approves, while their details are being taken.
Which auctions these rules reach
Sections 24J and 24K apply to auctions of residential land, which the Act defines. It covers land with one or two homes on it, built or being built, and no other improvements; vacant land where a home may lawfully be built; a community or strata lot or unit that is a single home; and an exclusive right to occupy a single home. It leaves out land used wholly for non-residential purposes and land of more than 2.5 hectares, or another area the regulations prescribe.
What the person bidding brings
Land and Business (Sale and Conveyancing) Regulations 2025, regulation 27
Regulation 27 turns the Act’s requirement into a short list. Before a person bidding for someone else is entered in the register, the agent must have:
- Their own proof of identity. A driver’s licence, passport, credit or debit card, a gas, electricity or telephone account, or a similar document or card issued to them.
- A written authority to bid, signed by the buyer.
- Proof of the buyer’s identity, from the same kinds of document, or, where the buyer is a body corporate, its certificate of incorporation.
The authority and the buyer’s proof of identity need not be originals. A photocopy, a fax or a scanned copy of the original will do.
Illustrative example, not a real saleA buyer who will be overseas on auction day asks a sibling to bid. Before the auction the sibling shows the agent their own driver’s licence, a letter the buyer signed authorising them to bid, and a scanned copy of the buyer’s passport. Each of those is a document regulation 27 names, and the scan is a copy it allows.
On the day
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A late arrival stops the auction
If someone who was not in the register when the auction began is to be allowed to bid, the auction must be interrupted while their details are entered. The same identity and authority rules apply to them.
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Every bid carries an identifier
The auctioneer may take a bid only from someone in the register, with the register in hand, who is displaying the unique identifier allocated to them for the auction. That identifier can be a number, a letter, a colour or some other identifying feature. When taking the bid, the auctioneer must say aloud that it came from the bidder with that identifier.
An auctioneer who refuses a bid because these conditions are not met is not liable to anyone for refusing.
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The record keeps pace
The amount of each bid goes into the auction record as it happens, with the identifying number of the person who made it, except that a bid the auctioneer makes for the seller is recorded as a vendor bid.
The details given for that record have to be true. Giving details for the auction record that a person knows, or has reason to believe, are false in a material particular is an offence, with a maximum penalty of $10 000 in the version of the Act dated 15 January 2026.
Who gets to see the buyer’s name
Anyone who made the auction record, or had access to it, must not disclose or use what it holds except as Part 4A of the Act allows or an authorised officer requires. Regulation 27(3) then sets out exemptions to that rule, so the two are read together.
If the land sells at the auction
The purchaser’s full name and address and the price go into the auction record.
If it is passed in
Where the auctioneer negotiates on the same day with a person who bid, or for whom a bid was made, that person’s name and address and every amount they offer are recorded, and so is the price if a sale follows that day.
That same-day contract after a pass-in also has no cooling-off period when it is made with someone who bid, or on whose behalf a bid was made.
After the hammer, and if a rule is broken
SA.GOV.AU says auction sales are unconditional, so buying at one takes extensive preparation, and that whoever wins is expected to sign the contract and pay a deposit as soon as the auction ends, usually at least 10% of the winning bid.
A breach of section 24J does not undo a bid or the contract for the land, and neither does an auctioneer taking a bid in breach of section 24K.