Here's the thing about an auction room that most people don't appreciate until they've been in one: it doesn't care how you feel about the number you just bid. The hammer falls, and in that instant you own the property. A 10% deposit is due before you leave the room. You've got 28 days to find the rest, and nobody is waiting on your survey, your solicitor's holiday, or a change of heart.
To be fair, I like that about auctions. There's no chain, no gazumping, no seller quietly entertaining a better offer behind your back. But the same certainty that makes auctions attractive is exactly what catches people out. You've probably already worked out why the speed and the price appeal to you. So I won't spend long on that. What I want to walk through instead is the part most guides skip over: how the pricing signals actually work, why your usual mortgage broker can't help you here, and where the money quietly disappears for buyers who think they've done their homework.
What you're actually signing up for
The moment your bid wins, three things become due that day, before you leave. There's the 10% deposit, non-refundable. There's the auctioneer's admin fee, usually somewhere between £600 and £1,500 including VAT. And there's whatever buyer's premium is sitting in the lot particulars, which varies from lot to lot and is easy to miss if you haven't read carefully. None of it comes off the purchase price. All of it is on top.
Then there's the guide price, and I'd encourage you to think of it less as a number and more as bait, in the friendliest possible sense. It exists to get you interested enough to download the legal pack. The figure that actually matters is the reserve, the seller's genuine floor, which nobody discloses but which the rules do constrain. Publish a single guide figure and the reserve can't sit more than 10% above it. Publish a range instead, and the reserve has to fall somewhere inside it. Once you know that, a guide price stops being mysterious. It becomes a maths problem you can solve before you ever set foot in the room.
The legal pack matters more than any of this, and it's worth being honest about what it is and isn't. It exists to satisfy minimum disclosure rules, not to look out for you. Title, searches, special conditions, leasehold detail, all of it needs reading properly before you bid, because there's no reading it properly afterwards. Special conditions in particular are where sellers tuck in costs you weren't expecting: their legal fees, search fees, occasionally an uncapped premium that changes your real maximum bid the moment you spot it. If something in the pack looks thin or vague, ring the vendor's solicitor and ask. Silence in a legal pack rarely means there's nothing to say.
One more thing worth knowing before auction day: there are two distinct formats, and mixing them up is an easy mistake to make. A traditional, unconditional auction binds you the second the hammer falls, with 28 days to complete, no extensions, every calendar day counted including weekends and bank holidays. The Modern Method, sometimes called conditional auction, gives you longer: 56 days in total, roughly 28 to exchange and a further 28 to complete, secured with a reservation fee of 4 to 5% plus VAT rather than a full deposit on the day. That extra time is what lets ordinary mortgage buyers take part. It also means you're not legally secure until exchange, so someone with deeper pockets can still outbid you while you wait for your mortgage offer to land.
The financing maths that trips people up
Here's the arithmetic that catches out even sensible buyers. A standard mortgage takes 6 to 12 weeks from application to completion. A traditional auction gives you 28 days. Those two numbers were never going to meet in the middle, and no amount of urgency with your bank or solicitor changes that. If your funding plan assumes a normal mortgage will land inside the auction window, you don't actually have a funding plan. You have a hope.
This is why anyone serious about buying at auction arranges bridging finance, before they ever raise a paddle. It exists precisely for this situation: short-term, secured against the property, typically up to 75% loan-to-value, and, when the groundwork's been done properly in advance, capable of completing in a short timeframe. By groundwork I mean terms already agreed, a solicitor already instructed, a valuation ideally arranged against this specific lot, not a general one. Skip that preparation and you're asking a lender to compress weeks of underwriting and legal work into days, usually at a premium, with no real guarantee it lands in time to save your deposit.
Bridging costs more than a mortgage, and I think that's worth saying plainly rather than dressing up. That cost buys you speed and certainty, which is precisely what you need in this situation, so it isn't money wasted. It is, however, a short-term tool with a single job: getting you to your exit. That exit is either a refinance onto a normal mortgage once the property has a valuation or a trading history to support one, or the sale proceeds if your strategy all along was to buy, improve, and sell. Decide which one applies to you before you bid, not after you've won. A bridge with no clear way out is how a genuinely good auction purchase turns into a forced sale a few months later.
Get a proper Agreement in Principle sorted before auction day. Not a friendly chat with your usual bank, an actual AIP from a lender who understands how auctions work. It does two useful things at once. It turns you from a hopeful bidder into someone the auctioneer can trust will actually complete, and it tells you, honestly, what your real ceiling is before the bidding starts, which matters a great deal more than whatever guide price is printed in the catalogue and top budget figure you had in mind.
Do all of this before you bid, never after
There's no survey period once the hammer's down. No renegotiating the price. No walking away without losing your deposit. So everything that matters has to happen now, while you still can.
Start with the legal pack, every page of it, ideally with a solicitor who's done this before and can turn a review round in days rather than weeks. Get eyes on the property too, and professional ones if you can arrange it. Auction stock is frequently distressed, tenanted, or structurally compromised, which is often exactly why it ended up here rather than on the open market, so a guide price that looks suspiciously good is a reason to look harder, not relax.
Build your real maximum bid from what the legal pack tells you, not from the guide price on the listing. Admin fee, premium, any costs the seller has pushed onto the buyer, lease extension or dilapidations liability, all of it needs adding before you settle on a number you're comfortable with. And check, properly, that your funding can complete inside the actual deadline: a lender who already knows this specific lot, a valuation already booked, a solicitor already instructed. "I'll sort the money once I've won it" has ended more auction purchases than almost anything else.
Where even experienced buyers still get burned
It's rarely inexperience that catches people out at this level. It's usually a small assumption that turned out to be wrong.
Bidding before financing is genuinely confirmed is the classic one. A friendly conversation with a lender isn't a facility, and if the money can't move on exchange day, you're gambling your deposit on a timeline you don't control. Missing the completion deadline is the more expensive mistake: you don't just lose your 10%, because if the seller resells for less, they can pursue you for the shortfall plus costs, and on a six-figure lot that's a genuinely serious liability, not a theoretical one.
Then there's mistaking the guide for something close to a valuation, which trips up buyers who really should know better. Properties routinely sell 15 to 25% above guide once real bidding opens, so the guide only ever tells you where the floor is, never where the ceiling sits. And skipping the legal pack because the auction is close, usually under time pressure, is how short leases, restrictive covenants, and undisclosed costs surface after completion rather than before it, when it's far too late to do anything about them.
The last one is having no exit for the bridge. If you can't say, clearly, how and when it gets repaid, refinance or sale, you haven't actually finished the deal. You've just postponed the difficult part of it.
Treat the 28 days as the real deadline it is, not a formality you can talk your way around, and get the financing arranged before the gavel rather than after. Do that, and auction stock remains one of the sharpest ways to buy property in this market. Get the sequence wrong, and the deposit you lose will have paid, expensively, for the lesson.
Buying at auction? Talk to us before you bid.
Auction finance: common questions
How can I avoid losing my auction deposit if my finance falls through?
Get your finance sorted before you bid, not after. Talk to a broker before auction day and read the legal pack properly, as extra fees and title problems are more common than people think. Even with credit approval, completion isn't guaranteed. The lender still has to be happy with the property itself and that the numbers work, and only then will it release the money. That's why paying for a valuation before you bid makes sense. It might cost a few hundred pounds or a few thousand, depending on the value and type of property, but that's small next to losing a 10% deposit. If there's no time for a surveyor to visit, ask your broker for a lender that will accept an automated valuation.
What happens to my 10% deposit if my finance does not complete in time?
If you can't complete by the deadline, which is usually 28 days, you're in breach of contract. The seller can normally keep your deposit and may come after you for more if they resell for less. Some sellers will agree a short extension, but usually with daily interest or penalties on top, so don't count on it.
Can I arrange auction finance before the auction so I know my budget?
Yes, and it's the smart way to do it. A lot of bridging lenders now use automated valuations to speed things up. As there's no need for a physical inspection, some can get you to full credit approval before auction day, so you walk in knowing exactly what you can borrow and how much you need to put in. Not every lender will use one for every property, so check with your broker first.
What deposit do I need on the day if I am using auction finance?
Most auctions want 10% of the price on the day, plus the auctioneer's fee. Bridging lenders usually go up to around 70 to 75% of the property's value, depending on how it's valued, so the rest of the price and your costs need to come from your own money. A few lenders will look at lending against the real market value if you're buying at a genuine, provable discount, but that's decided case by case, so don't build your budget around it.
How quickly can bridging finance complete for an auction purchase?
Most bridging lenders can complete in 10 to 14 working days once the legal pack, valuation and solicitor are lined up. The key is to start before auction day, not after the hammer falls. An Agreement in Principle, solicitor instructed and a valuation booked against the specific lot puts you in a position to move fast.
What happens if I can't complete within 28 days?
You risk losing your 10% deposit. If the seller resells for less, they may also pursue you for the shortfall plus costs. This is why funding should be pre-arranged and your solicitor should be confident the legal pack can be reviewed quickly.
Can I use a normal mortgage instead of bridging finance?
A standard mortgage rarely completes inside 28 days. Auction purchases are normally funded with bridging finance first, then refinanced onto a term mortgage once the property is ready and the lender has the time it needs to underwrite fully.
What does the guide price actually mean?
The guide price is a marketing figure. The reserve, which is not disclosed, must sit within 10% of a single guide price or inside a published guide range. Use the guide to understand the seller's floor, not the likely selling price, and build your maximum bid from the legal pack and your funding limit.
What should I check in the legal pack before bidding?
Read the title, searches, special conditions and leasehold details carefully. Watch for buyer-paid legal fees, premiums, uncapped charges, lease extension liabilities or restrictive covenants. If anything is vague, contact the seller's solicitor before the auction.