The 28-Day Completion Rule: How Auction Finance Works in the UK

Twenty-eight days. That's what you get when you win at a property auction in the UK.

Not 28 working days. Not "roughly a month." Exactly 28 calendar days from the fall of the hammer to completion. Miss that deadline and you're not just inconvenienced—you're potentially facing the loss of tens of thousands of pounds and legal action.

This 28-day rule is what makes auction purchases fundamentally different from normal property buying, and it's why specialist auction finance exists in the first place. Standard mortgages simply cannot complete within this timeframe. Bridging finance can—but only if you understand the process and plan accordingly.

In this article, we're going to break down exactly how the 28-day rule works, why it exists, what happens during those 28 days, and most importantly, how to make sure you meet the deadline without losing your deposit.

Why Does the 28-Day Rule Exist?

Before we dive into the mechanics, it's worth understanding why auctions work this way.

Certainty for Sellers

Auction sellers want speed and certainty. They don't want to wait months for buyers to arrange mortgages, only for deals to fall through at the last minute. By compressing everything into 28 days and making the contract binding immediately, sellers get certainty that the sale will complete.

Efficiency for the Market

Properties that might take 4-6 months to sell conventionally can be sold, completed, and off the market within a month at auction. This benefits everyone: sellers get their money, buyers get their property, and the market moves efficiently.

Weeding Out Uncommitted Buyers

The 28-day deadline ensures that only serious, well-prepared buyers participate. If you can't arrange finance and complete quickly, you shouldn't be bidding. It's that simple.

The trade-off for sellers? They usually accept lower prices than they'd get on the open market, because speed and certainty have value.

What Exactly Happens on Auction Day?

To understand the 28-day timeline, you need to know what happens the moment you win.

The Hammer Falls

Your bid is accepted. The auctioneer confirms you as the buyer. Congratulations—you've just entered into a legally binding contract.

You Sign the Memorandum of Sale

Within minutes, you'll be asked to sign a document confirming your winning bid. This isn't a preliminary agreement. It's not subject to contract. It's a binding commitment.

You Sign the Full Contract

Unlike normal property purchases where exchange of contracts happens weeks after your offer is accepted, at auction you're exchanging contracts immediately. You sign the same contract the seller has already signed. It's now legally binding on both parties.

You Pay the 10% Deposit

On the spot—usually by debit card or banker's draft—you pay 10% of the purchase price. This money is non-refundable if you fail to complete.

You Receive Your Copy of the Contract

You get a copy of the signed contract and the legal pack. You now legally own the property—you just haven't paid for it yet or taken possession.

And that's it. The whole process takes maybe 10 minutes. And in those 10 minutes, you've committed to finding the remaining 90% of the purchase price and completing within 28 days.

The 28-Day Timeline: What Needs to Happen and When

Let's walk through a realistic 28-day timeline from auction day to completion, so you understand what needs to happen and when.

Days 0-1

Immediate Actions

Auction day: Sign contract, pay deposit, receive legal pack
Immediately contact your bridging lender to confirm you won
Forward the signed contract and legal pack to your solicitor
Confirm all your details are correct and all parties are ready to move

Days 2-5

Valuation

The lender arranges for a chartered surveyor to inspect and value the property
The surveyor visits the property (you'll need to give access if possible)
The valuation report is completed and sent to the lender

Critical note: The valuation is based on the property's current condition. If you're buying a property needing work, don't expect the valuation to reflect its post-refurbishment value.

Days 6-10

Underwriting and Formal Offer

The lender's underwriters review the valuation, your application, and your exit strategy
They assess the risk and decide on final terms
You receive a formal loan offer with all terms, conditions, and fees
You review, sign, and return the offer

Days 11-21

Legal Work

Your solicitor and the lender's solicitor handle all the legal documentation
They'll review the title, prepare the mortgage deed, arrange Land Registry searches
All security paperwork is finalised

This is often the longest part of the process, which is why using a fast, experienced solicitor matters so much.

Days 22-26

Final Preparations

All legal work should be completed by this point
Final checks are made
The lender prepares to transfer funds
Your solicitor confirms everything is ready for completion

Days 27-28

Completion

The lender releases funds to your solicitor
Your solicitor transfers the balance to the seller's solicitor
Completion occurs
You receive confirmation and can collect the keys

That's the ideal timeline. In reality, various steps can take longer or shorter depending on the complexity of the property, responsiveness of all parties, and whether any issues arise.

What If the Valuation Comes in Low?

This is one of the most common curveballs in auction purchases. You bid £200,000, thinking you got a great deal. The lender's surveyor values the property at £180,000. Now what?

How This Affects Your Loan:

If the lender was offering 75% LTV, they were planning to lend:

75% of £200,000 = £150,000

But now they'll lend:

75% of £180,000 = £135,000

You still owe the seller £200,000. You've paid £20,000 as a deposit. You need to find:

£200,000 - £20,000 - £135,000 = £45,000 additional funds

If you don't have that extra £45k, you're in trouble.

How to Avoid This Problem:

1.Be realistic about property values before you bid
2.Don't get carried away in bidding wars
3.Discuss likely valuations with your lender before auction
4.Have contingency funds available in case of down-valuation
5.Conservative bidding protects you from valuation surprises

Can You Extend the 28-Day Deadline?

Technically, yes—but only if the seller agrees.

Some sellers are flexible, especially if completion is imminent and you just need a few extra days. Others are rigid and will forfeit your deposit on day 29 if you haven't completed.

How to Request an Extension:

Contact the seller's solicitor immediately (not on day 27—do it early)
Explain the situation honestly (e.g., "valuation delayed by three days, we're otherwise ready")
Offer to pay daily interest or fees as compensation
Get any agreement in writing

But don't count on extensions.

Many auction sellers are selling at auction precisely because they need speed and certainty. Asking for more time defeats the purpose. Plan to complete on time. If you get an extension, treat it as a bonus, not an expectation.

What If You Absolutely Cannot Complete in 28 Days?

Let's talk worst-case scenario. It's day 25, and you know you can't complete. Maybe your lender pulled out. Maybe legal issues emerged. Maybe you've run out of money. What now?

Option 1: Pull Together Emergency Funds

Can you borrow from family, use credit cards, take out a personal loan—anything to scrape together the shortfall? It's expensive and stressful, but it's better than losing your deposit.

Option 2: Find Alternative Finance Immediately

If your original lender backed out, contact other bridging lenders urgently. Some specialise in last-minute rescues. They'll charge premium rates, but again—better than losing £20k+.

Option 3: Negotiate with the Seller

Be upfront. Explain the situation. Offer to forfeit part of your deposit in exchange for releasing you from the contract. Some sellers will take £5k immediately rather than go through the hassle of reselling.

Option 4: Accept You're Losing Your Deposit

If you absolutely cannot complete and there's no way out, you'll lose your 10% deposit. Don't compound the problem by ignoring it. Communicate with the seller's solicitor, accept the loss, and move on.

Option 5: Complete and Immediately Resell

If you can somehow scrape together completion funds—even if it means short-term expensive finance—complete the purchase. Then immediately resell. Yes, you'll pay stamp duty, legal fees, and agent fees. But you won't lose your deposit or face lawsuits.

Obviously, none of these options are good. The lesson? Don't bid at auction unless you're certain you can complete.

How Fast Can Auction Finance Actually Complete?

We've talked about the 28-day deadline, but how fast can auction finance realistically complete?

Best case: 10-14 days

When everything aligns—standard property, clean legal title, fast valuation, experienced solicitors, responsive borrower—completion can happen in under two weeks.

Typical case: 18-23 days

Most auction purchases complete somewhere in this range. Not the full 28 days, but not lightning-fast either. This is realistic when there are no major complications.

Slower case: 25-28 days

If there are valuation delays, legal complications, or slow solicitors, you might be cutting it fine. This is uncomfortable but still achievable.

Red flag: Still working on day 24+

If you're on day 24 and major steps aren't complete yet (e.g., still waiting for valuation, formal offer not issued), you're in danger. Act urgently.

The key is front-loading as much work as possible. Get your lender lined up pre-auction. Have your solicitor review the legal pack beforehand. Arrange surveys in advance if possible. The more prep work you do, the more buffer you have in the 28 days.

Why Some Buyers Complete in 10 Days and Others Struggle

Not all auction purchases are created equal. Some sail through in 10 days. Others barely scrape in on day 28. What's the difference?

Fast Completions Happen When:

•The buyer had finance pre-approved before bidding
•The property is standard residential in good condition
•The legal title is clean with no complications
•The buyer's solicitor specialises in auctions and bridging
•The lender is efficient with fast underwriting
•Everyone involved communicates proactively

Slow Completions Happen When:

•The buyer starts arranging finance after winning
•The property is non-standard or has issues
•Legal complications emerge (short leases, covenants, disputes)
•The solicitor doesn't understand urgency
•The lender is slow or bureaucratic
•People wait for others to chase them rather than being proactive

The pattern is clear: preparation and proactivity determine speed.

Can You Use Auction Finance for Properties in Scotland?

Yes, but be aware that Scottish property law differs from England and Wales, including auction procedures.

In Scotland:

•Auctions are less common for residential property
•When they do occur, contracts may exchange differently
•Legal processes differ
•Completion timelines may vary

Most bridging lenders, including Black Props, cover Scotland—but make sure you mention it's a Scottish property upfront so the lender can account for legal differences.

How to Give Yourself the Best Chance of Meeting the Deadline

Let's finish with practical advice: what can you do to ensure you complete within 28 days?

Before Auction:

1.Get a decision in principle from a bridging lender
2.Have your deposit funds immediately available
3.Line up an auction-specialist solicitor
4.Read the legal pack (or pay a solicitor to review it)
5.Calculate your maximum bid including all costs

After Winning:

1.Contact your lender and solicitor within 24 hours
2.Respond immediately to any requests for documents or information
3.Check in daily with your solicitor for progress updates
4.Keep a timeline tracking what's been completed and what's outstanding
5.Aim to complete by day 26, not day 28

What Not to Do:

✗Don't wait for people to chase you
✗Don't assume "it'll be fine"
✗Don't leave everything to the last minute
✗Don't use a generalist solicitor who doesn't understand auction urgency
✗Don't arrange finance after you've won

The Bottom Line: Respect the 28 Days

The 28-day completion rule isn't arbitrary. It's there for a reason, and it's non-negotiable. Auctions offer incredible opportunities to buy property below market value, but only for buyers who understand the process and prepare accordingly. If you respect the deadline, line up your finance in advance, and work with experienced professionals, completing within 28 days is entirely achievable. But if you think you can wing it or that the rules don't really apply to you, you're setting yourself up for an expensive lesson. Know what you're getting into, be honest about your readiness, and never bid at auction unless you're absolutely certain you can complete.