Most attention at a property auction goes to the guide price and the property itself. Yet the auction deposit and completion terms are where the real financial commitment sits. The moment the hammer falls at an unconditional auction, you have exchanged contracts: the deposit is payable immediately and the completion clock starts running. Buyers who understand exactly how much is due, when it is due and what the contract says about completion are in a far stronger position than those who discover the detail afterwards. This guide explains how auction deposits and completion timetables work in the UK, where the special conditions of sale can change the standard position, and the checks worth making in the legal pack before you bid.
The Auction Deposit: The Standard Position
At a traditional unconditional auction, the fall of the hammer constitutes exchange of contracts. The successful bidder is then required to pay a deposit — normally 10% of the purchase price — on the day of the auction. Most auction houses also apply a minimum deposit figure, commonly in the region of £5,000, which matters on lower-value lots where 10% would fall below that threshold.
Payment is usually required in cleared funds. In practice that means bank transfer, debit card or, for in-room auctions, occasionally banker’s draft. Cash is rarely accepted in meaningful amounts due to anti-money laundering rules, and buyers should expect identity and source-of-funds checks before or on auction day. Arranging these requirements in advance is a routine point to deal with rather than a complication: registering with the auctioneer early and confirming acceptable payment methods removes any friction on the day.
Where the Special Conditions Can Change the Deposit Terms
The general conditions of sale set the default framework, but the special conditions of sale attached to each lot can vary it, and frequently do. On the deposit specifically, points worth confirming in the legal pack include the deposit percentage (some special conditions increase the deposit above 10%, or apply a fixed minimum higher than the auction house standard), who holds the deposit (a deposit held as stakeholder is retained neutrally until completion, whereas a deposit held as agent for the seller can be released to the seller immediately — which carries more practical risk for the buyer if the transaction later fails through the seller’s default), and additional sums payable on the day (buyer’s administration fees, auctioneer charges and contributions to the seller’s costs are often payable alongside the deposit and can add materially to the day-one cash requirement).
None of these points is unusual, and none should be treated as adverse by default. They are, however, exactly the kind of detail a legal pack review should surface before bidding, because they affect both the cash you need available on auction day and the true cost of the purchase.
Completion Timescales: What the Contract Usually Says
The standard completion period at most UK auctions is 28 days from exchange, with 14 or 20 business days also common. The precise deadline is set by the contract — usually in the special conditions — and it is a fixed contractual date rather than a target. Some lots complete on shorter timescales, particularly repossessions or lots where the seller wants a fast exit; others occasionally allow longer, for example where the seller needs time to complete a related transaction.
The key discipline for any bidder is simple: confirm the completion date in the legal pack before the auction, not after. A 14-day completion is entirely workable for a cash buyer or a buyer with bridging finance agreed in principle, but it is a demanding timetable for a buyer relying on a standard mortgage application started from scratch.
What Happens If Completion Is Delayed
If the buyer does not complete on the contractual date, the standard machinery is measured but firm. Interest typically accrues on the outstanding balance at the contract rate — often around 4% above base rate — from the contractual completion date. The seller may also serve a notice to complete, which usually gives ten working days to complete and makes time of the essence.
If the buyer still fails to complete after a valid notice, the seller is generally entitled to rescind the contract, forfeit the deposit and resell the property, with the ability to claim any shortfall and costs from the defaulting buyer. This is not a reason to avoid auctions; it is a reason to ensure funding is genuinely in place before bidding. For well-prepared buyers, the completion timetable is simply a known parameter to plan around.
Funding the Deposit and Completion: Practical Realities
Because the timetable is contractual, the funding route needs to match it. Cash buyers have the most flexibility and are well suited to short completion periods, subject only to having funds liquid and source-of-funds evidence ready. Bridging finance is the most common route for auction purchases on standard timescales — decisions in principle can usually be obtained before auction day, and reputable bridging lenders are accustomed to 14 to 28-day completions. Standard buy-to-let or residential mortgages can work within 28 days, but generally only where the application, valuation and legal work are substantially progressed before the auction. Relying on a mortgage that has not yet been applied for is the main avoidable cause of missed completions.
Whichever route applies, the deposit itself almost always needs to come from the buyer’s own resources on the day, since lending is normally drawn at completion rather than exchange.
Buyer Costs Beyond the Deposit
The deposit is the largest day-one payment but rarely the only one. A realistic auction budget should also allow for the auctioneer’s administration or buyer’s fee, any buyer’s premium attached to the lot, reimbursement of the seller’s legal or search costs where the special conditions require it, stamp duty land tax payable after completion, and the buyer’s own legal and due diligence costs. Unusually high seller cost reimbursements occasionally appear in special conditions and are worth identifying early, because they effectively increase the purchase price and should be priced into the maximum bid rather than discovered afterwards.
Conditional Auctions: A Different Deposit Structure
The modern method of auction, common on online platforms, works differently. Instead of exchanging contracts on the fall of the hammer, the buyer pays a reservation fee — typically around 4 to 5% of the price with a fixed minimum — and enters a reservation period of usually 28 days to exchange and a further 28 days to complete. The reservation fee is normally non-refundable and often sits on top of the purchase price rather than counting towards it. Neither structure is inherently better; they simply place the commitment point and the cash requirement at different stages, and the legal pack and auction terms will state clearly which applies.
Checking Deposit and Completion Terms Before You Bid
All of the points above are visible in advance. A proper review of the auction legal pack before bidding should confirm the deposit percentage, any minimum figure, and whether it is held as stakeholder or agent; the contractual completion date and whether it suits your funding route; all additional fees and seller cost reimbursements payable on or after auction day; whether the sale is unconditional or conditional and what that means for when you are committed; and any special conditions varying the standard interest rate, notice provisions or completion mechanics.
Treated this way, the deposit and completion provisions stop being a source of risk and become part of the deal arithmetic: known figures, on known dates, priced into the bid. That is the position every auction buyer should be in before raising a hand or clicking confirm.