The online property auction has moved from novelty to mainstream. A significant share of UK auction lots now sell through timed online sales or livestream events rather than a hotel ballroom, and for investors the format offers real advantages: wider access to stock, the ability to bid from anywhere, and a clear digital record of the process. What has not changed is the legal substance. An online property auction in the UK carries the same binding commitments, the same legal pack and the same deposit and completion mechanics as a traditional room auction. This guide explains how the legal process works online, where the formats differ, and what to check before you place a bid.

How an Online Property Auction Works

Most online property auctions in the UK run as timed sales. Each lot has a published start and end time, bidders submit bids through the auctioneer’s platform, and the highest bid at the close wins, provided the reserve has been met. Many platforms use a bid-extension rule: a bid placed in the final minutes extends the countdown, which prevents last-second sniping and means the closing time is a minimum, not a guarantee.

The other common format is the livestream auction, where an auctioneer conducts the sale in real time and bidders participate online, by phone or by proxy. Legally, both formats work the same way as a room auction: when the (virtual) hammer falls or the timer closes on an unconditional sale, a binding contract is formed on the terms set out in the legal pack.

Before registering for any online property auction, confirm which method of sale applies to the lot. The distinction determines when you become legally committed and what you pay on the day.

On an unconditional sale (the traditional method), exchange of contracts happens at the close of bidding. You pay a deposit — typically 10 per cent — immediately, and completion usually follows within 28 days. Withdrawal after the close means losing the deposit and potential liability for the seller’s losses.

On a conditional sale (the modern method), the close of bidding grants a reservation period, commonly 28 days to exchange and a further 28 days to complete. You pay a reservation fee — often around 5 per cent of the price subject to a minimum — which is usually non-refundable and, on many platforms, payable in addition to the purchase price.

Online platforms use the conditional method more heavily than traditional room auctions, so this is a point to confirm before you bid rather than after. The reservation fee structure materially affects your true acquisition cost and should be priced into any bid limit.

Whatever the format, the auction legal pack remains the contractual foundation of the sale. On an online platform the pack is normally available to download once you register interest, and it typically contains the title register and plan, the special conditions of sale, searches where the seller has provided them, replies to standard enquiries, any tenancy documents and the EPC. Reviewing the legal pack before bidding is the single most important step in property auction due diligence, because bidding online makes commitment fast and convenient while the obligations remain exactly as binding.

Two points deserve particular attention in the online context. Special conditions of sale frequently pass costs to the buyer — such as the seller’s legal fees, search costs, arrears or auctioneer charges — and they vary lot by lot and platform by platform, so read them for every lot rather than assuming a standard position. Addendum updates also require attention: online packs are sometimes updated close to the end of the bidding window, so check the platform for late additions before placing a final bid, as an addendum forms part of the contract.

Registration, Identity Checks and Bidder Security

Online auctioneers must complete anti-money-laundering checks before allowing you to bid. Expect to verify your identity digitally, register a payment card and, on many platforms, authorise a bidder security hold or pre-authorisation against the card. If you intend to buy through a limited company, register in the correct name from the outset — amending the buyer entity after the close is at the seller’s discretion and can be treated as a variation of contract.

Registration usually closes before the lot ends, and identity checks can take more than a day to clear. Registering early protects your ability to bid and gives you the full window to complete your legal pack review.

What Happens When the Timer Ends

On an unconditional online sale, the close of bidding is the exchange of contracts. The platform takes the deposit from your registered card or requires prompt bank transfer, the contract is signed electronically or by the auctioneer on both parties’ behalf, and the completion countdown starts immediately. This is the same unconditional auction exchange that occurs in a room sale — the digital setting changes the mechanics, not the effect.

On a conditional sale, the close of bidding triggers payment of the reservation fee and starts the reservation period. You then instruct your solicitor, arrange finance and proceed to exchange within the agreed window. The conditional route offers more time, but the reservation fee is at risk if you withdraw, so the review work still belongs before the bid, not after it.

Deposits, Fees and Completion Timescales

The financial mechanics of an online property auction are worth setting out clearly, because they differ between platforms and directly affect returns. On unconditional sales, a deposit of typically 10 per cent is payable at the close of bidding. On conditional sales, a reservation fee of commonly around 5 per cent (subject to a minimum, often several thousand pounds) is charged, frequently on top of the purchase price. Many auctioneers also charge a fixed buyer’s administration fee per lot — the amount appears in the special conditions or the platform’s terms. The special conditions should also be checked for any obligation to reimburse the seller’s legal or search costs.

Completion usually follows within 28 days on unconditional sales, and within up to 56 days from the close on conditional sales, though the special conditions can shorten or extend either. None of these items is a reason to avoid online auctions — they are matters to price into the deal. An accurate view of total acquisition cost, including fees and recharges, is what separates a disciplined bid limit from an optimistic one.

Practical Checklist Before Bidding Online

A short sequence of checks puts most online auction purchases on a solid footing. Confirm the method of sale — unconditional or conditional — and the fee structure for the lot. Download the full legal pack and have it reviewed before you register a bid, focusing on title, special conditions, tenancies and searches. Check for addendum documents on the platform close to the end of bidding. Line up finance appropriate to the completion timescale, including bridging where a 28-day deadline is realistic only with pre-arranged funding. Register and clear identity checks early, in the correct buying entity. Set a bid limit that reflects total acquisition cost, and let the timer close without you if bidding passes it.

Handled this way, the online format is not a riskier way to buy at auction. For a prepared investor it is often a more transparent one, with the pack, the terms and the bidding history all in one place.