Auctions look like the fast lane of property buying: no chains, no months of conveyancing drift, a gavel, a deal. For a first-timer, that speed is exactly the danger. At a traditional auction, the fall of the hammer is exchange of contracts. There is no cooling-off period, no renegotiation after a bad survey, and no walking away because your mortgage fell through. Everything that would normally happen after you agree a purchase — survey, legal checks, finance — has to happen before you bid, or not at all.
This guide walks through how UK property auctions actually work, the two methods that matter, how to read a legal pack, what the whole purchase really costs, and the mistakes first-timers make most often. It is general information, not legal or financial advice. Take a solicitor through the legal pack and a broker through the finance before you bid on anything.
The short answer
There are two auction methods in the UK, and confusing them is the most expensive first-timer mistake. At a traditional (unconditional) auction, the winning bid exchanges contracts immediately: you pay a 10% deposit on the day and normally complete within 28 days. At a modern method (conditional) auction, usually run online, the winning bidder pays a non-refundable reservation fee — typically around 4.5% to 5% of the price, often with a minimum of several thousand pounds including VAT — and then has around 56 days in total to exchange and complete. The modern method gives you time to arrange a mortgage; the traditional method does not, unless your finance is already fully in place.
Either way, the rule that governs everything else is the same: do your due diligence before you bid, set a maximum bid that includes every fee and repair cost, and never bid above it in the heat of the room.
Traditional vs modern method: the decision that shapes everything
| Traditional (unconditional) | Modern method (conditional) | |
| Commitment | Binding at the fall of the hammer — contracts exchange immediately | Binding on exchange, after you pay the reservation fee |
| Money on the day | 10% deposit, usually with a minimum (often £3,000) | Non-refundable reservation fee, typically around 4.5%–5% of the price, on top of the price |
| Time to complete | Normally 28 days from the auction | Normally around 56 days in total (about 28 to exchange, 28 more to complete) |
| Mortgage | Must be fully arranged before you bid, or use cash / bridging | Time to arrange a mortgage after winning, but the fee is lost if you pull out |
| Who it suits | Cash buyers and buyers with finance already agreed | Buyers who need mortgage time but accept losing the fee if the deal fails |
Check the special conditions for the specific lot: some traditional auctions allow a longer completion period, and some modern-method sales have different exchange windows. The catalogue description is marketing; the conditions of sale are the contract.
Guide price, reserve price, and what a property will actually sell for
The guide price is the auctioneer's indication of where bidding is expected to start, or the range within which the property is marketed. It is not a valuation, and it is not a promise. The reserve price — the minimum the seller will accept — is usually undisclosed and is often set at or slightly above the guide. Bidding frequently finishes well above the guide, especially on lots that attract landlords and developers.
First-timer discipline: value the property yourself before the auction. Look at comparable sold prices for similar properties in the same street and postcode, not asking prices. Deduct the cost of repairs, the cost of any legal fix (a lease extension, for example, can cost tens of thousands), all fees and taxes, and your required margin if you are buying as an investment. That figure, not the guide price, is your maximum bid. If bidding passes it, stop — there will be another lot.
The legal pack: read it, or pay a solicitor to read it
The legal pack is the seller's bundle of documents, made available before the auction. A typical pack contains the conditions of sale, the title documents, and sometimes searches (local authority, drainage, environmental) and, for leasehold, the lease and management information. It may also contain special conditions that add costs: the buyer paying the seller's costs, arrears, or a contribution to the auctioneer's fee.
Read it with a solicitor, and check specifically for:
- Title problems. Restrictive covenants, rights of way, unregistered land, flying freeholds, and boundary disputes.
- Leasehold traps. Short remaining term, escalating ground rent, onerous service charges, and major works planned by the freeholder. A cheap flat with 62 years left on the lease is not cheap once the extension is priced in.
- Tenancies. A sitting tenant, a regulated tenancy, or an assured tenancy you cannot end quickly changes both value and strategy. Under the Renters' Rights Act, possession now runs only through Section 8 grounds — check the tenancy guide in this series before bidding on a tenanted lot.
- Planning and building issues. Unauthorised extensions, missing building regulations sign-off, and use-class problems. A loft conversion without sign-off can be unmortgageable until regularised.
- Searches not included. If the pack omits searches, you must commission your own before bidding — after the hammer falls, a bad search result is your problem.
Budget for a solicitor's pack review on every lot you seriously consider, even the ones you do not win. It is the cheapest money in auction buying: a £300 review that stops you buying a £150,000 problem is a bargain.
Surveys and viewings: the checks you cannot do afterwards
Attend the viewing, and take a builder or surveyor if the property needs work. Auction properties are often sold as seen, and the catalogue description may be brief or optimistic. Look for damp, subsidence cracks, roof condition, heating and electrical systems, and signs of structural movement. A pre-auction survey is the single most important piece of due diligence you can do, because after exchange there is no price reduction for anything the survey would have found.
Mortgageability is a separate check from condition. Some auction properties cannot be mortgaged in their current state — no working kitchen or bathroom, no heating, structural problems, or a lease too short for the lender. If you need a mortgage, get your broker to confirm, before the auction, that this specific property type and condition is acceptable to a lender, and that the offer can complete within the deadline. If it cannot, your options are cash or bridging finance, priced accordingly.
Finance: have it ready, or know exactly what it costs
Cash is the simplest route at a traditional auction: deposit on the day, balance within 28 days, no lender timetable to miss.
A buy-to-let mortgage needs to be agreed in principle and, ideally, offered before a traditional auction, with the valuer already briefed on the property. Many lenders will not meet a 28-day deadline from a standing start, and a valuation that comes in below the bid leaves you funding the gap in cash. The mortgage guide in this series explains the lender's rental-cover test (ICR) — run it on the achievable rent, not the agent's estimate, before you bid.
Bridging finance is the standard fallback: a short-term loan, typically up to 12 months, secured against the property, used to complete quickly and then refinanced or repaid from a sale. It is fast and expensive — arrangement fees, monthly interest well above term rates, sometimes an exit fee. Only use it with a credible exit (a refinance offer, a sale, or cash reserves); bridging without an exit is how auction bargains become forced sales.
Modern method buyers have more time, but the reservation fee is non-refundable. If your mortgage falls through or the survey disappoints after you have paid it, the fee is gone. Treat it as money at risk from the moment you pay it, not as part of the deposit.
What the whole purchase really costs
Take a £150,000 winning bid at a traditional auction as an illustration. Your cash needed is not £150,000:
- Deposit on the day: £15,000 (10%), counting towards the price, not on top of it.
- Balance on completion: £135,000.
- Buyer's administration or premium fee: charged by the auction house on top of the price — check the catalogue, as it varies by auctioneer and can run into thousands of pounds.
- Solicitor and conveyancing costs: for the pack review, completion and registration.
- Survey costs: paid before the auction, win or lose.
- Stamp Duty Land Tax (SDLT): payable within 14 days of completion. In England and Northern Ireland, a buy-to-let purchase attracts the standard SDLT bands plus a 5% additional-dwellings surcharge; on a £150,000 buy-to-let that means 5% on the first £125,000 (£6,250) and 7% on the remaining £25,000 (£1,750), a total of £8,000. Use HMRC's calculator for the exact figure on your price, and remember Scotland (LBTT) and Wales (LTT) have their own equivalents.
- Insurance: from exchange, the property is at your risk. Put buildings insurance on risk immediately on winning a traditional auction, before you leave the room.
- Repairs and compliance: the refurbishment, safety certificates, EPC work and licensing costs that make the property lettable. The yield guide in this series explains why these belong in the bid price, not in a post-purchase surprise.
On a modern method purchase, add the reservation fee on top of the price — it is not deducted from it — and the same SDLT, legal, survey and repair costs.
On the day: bidding discipline
Register with the auctioneer in advance, bring proof of identity and funds, and confirm how the deposit must be paid — bank transfer or debit card, not cash, at most auction houses. Set your maximum bid in writing before you arrive, including all fees, tax and repairs, and bid in calm increments. Auction rooms are designed to make stopping feel like losing; stopping at your ceiling is the only way to guarantee you never overpay.
After you win: the 28-day (or 56-day) sprint
On a traditional win, you sign the memorandum of sale, pay the deposit and any buyer's fee, insure the property, and instruct your solicitor to complete within 28 days. Your solicitor handles the balance payment, SDLT return and Land Registry application. If you fail to complete on time, you risk losing the deposit and facing further liability for the seller's losses — the timetable must be planned from the outset, not discovered in week three.
On a modern method win, you pay the reservation fee, then exchange within the stated window (usually about 28 days) and complete within about 28 days after that. Use the window properly: mortgage valuation, survey if not already done, solicitor's full checks, and insurance — but remember the fee is already spent, so the window is for completing diligently, not for deciding whether you want the property.
First-timer mistakes, in order of cost
1. Bidding without reading the legal pack. The most expensive mistake, and the most common. 2. Bidding on the guide price instead of your own valuation. The guide is marketing, not a valuation. 3. Assuming a mortgage will be available after a traditional auction. It usually will not be, in time. 4. Forgetting the buyer's fee, SDLT and repair costs. A bargain at the hammer can be a loss after costs. 5. Ignoring leasehold and tenancy problems. Short leases, sitting tenants and service-charge arrears survive the auction and become yours. 6. Chasing the lot past your ceiling. There is always another auction. 7. Buying without insurance from exchange. Fire, flood or vandalism between exchange and completion is the buyer's risk.
Frequently asked questions
How much deposit do I need to buy at auction?
At a traditional auction, usually 10% of the purchase price on the day, often with a minimum of around £3,000. At a modern method auction, you pay a non-refundable reservation fee instead — typically around 4.5% to 5% of the price — on top of the purchase price.
Can I get a mortgage for an auction property?
Yes, but at a traditional auction the mortgage generally needs to be fully arranged before you bid, because completion is normally within 28 days. At a modern method auction you have around 56 days in total, which usually leaves time to arrange a mortgage — but the reservation fee is lost if you pull out.
What happens if I win at auction and then change my mind?
At a traditional auction you have exchanged contracts, so pulling out usually means losing your deposit and facing further liability. At a modern method auction you lose the non-refundable reservation fee and any auctioneer's fees already paid.
Related reading
- Buy-to-Let Mortgages for First-Time Landlords: Criteria, Deposits and Lenders (2026)
- How to Calculate Rental Yield: Gross vs Net (With UK Worked Examples)
- The Renters' Rights Act 2026: What Every Landlord Must Do Now
- Best Places to Invest in UK Property in 2026: Yields by Region
- How Much Deposit Do You Need for a Buy-to-Let in 2026?