Exchange to Completion: Deposit Forfeiture Risk Explained 2026/27

What Exchange of Contracts Actually Locks In

Exchange of contracts is the single most important legal moment in buying a home in England and Wales. Before exchange, either party can walk away at any time for any reason — this is why so many chains collapse in the weeks before exchange, sometimes at the last minute. Once contracts are exchanged, both sides are legally committed to the sale going ahead on the agreed completion date, on the agreed terms, at the agreed price.

At the point of exchange, the buyer's solicitor sends the deposit — traditionally 10% of the purchase price, though 5% is increasingly common by negotiation — to the seller's solicitor. This money is held, usually as a stakeholder, and its status changes immediately: it stops being a flexible part of your house-buying budget and becomes money the seller has a legal right to keep if you fail to complete.

The Deposit Forfeiture Risk in Practice

If a buyer exchanges contracts and then, for whatever reason, fails to complete on the agreed date — funds not in place, a change of mind, a mortgage offer withdrawn at the eleventh hour — the legal default position is stark: the seller can rescind the contract, keep the entire deposit, and put the property back on the market. If the seller's actual financial loss from the failed purchase (re-marketing costs, a lower price achieved on a resale, continued mortgage interest on their own onward purchase, legal costs) exceeds the deposit already forfeited, they can also sue the defaulting buyer for the balance.

Worked example: a buyer exchanges on a £350,000 purchase with a 10% deposit of £35,000. Three weeks later, the day before completion, their lender withdraws the mortgage offer because of a last-minute credit issue and the buyer cannot complete. The seller keeps the £35,000 deposit. If the seller then has to relist the property and eventually sells for £15,000 less six months later, plus £4,000 of additional legal, marketing and mortgage-related costs in the meantime, the seller's total loss is £19,000 — comfortably covered by the deposit already forfeited, so no further claim is likely. But if the shortfall had instead been £45,000, the seller could pursue the buyer for the extra £10,000 on top of the lost deposit.

This is the core reason mortgage brokers and solicitors push so hard to have your mortgage offer fully in place, with no outstanding conditions, before you agree to exchange. Use a Mortgage Calculator to sanity-check your affordability and monthly payment before committing to a completion date you might struggle to fund.

Typical Exchange-to-Completion Gaps

A same-day exchange and completion is the lowest-risk structure from a deposit-forfeiture perspective, because there's no window in which something can go wrong after you're contractually committed. The trade-off is that it leaves zero flexibility if a last-minute problem (funds not received, a bank transfer delayed) threatens completion day itself.

Covering a Funding Gap With Bridging Finance

Sometimes a buyer is contractually committed to a completion date but their own funds — most often the proceeds of a sale further down their chain — are not going to land in time. Rather than risk defaulting on the completion date and losing the deposit, some buyers arrange short-term bridging finance to cover the shortfall, complete on time, and repay the bridge once their own sale proceeds come through days or weeks later.

Worked example: a buyer needs £60,000 to complete alongside their mortgage, expected from the sale of their current home, but that sale is delayed by two weeks past the fixed completion date on their new purchase. A bridging loan of £60,000 at an illustrative rate of 0.9% per month costs roughly £540 for the two-week gap (calculated pro-rata), plus arrangement fees typically in the region of 1–2% of the loan amount. Against the alternative of losing a £30,000–£35,000 deposit and facing a potential further claim, the bridging cost is usually the far cheaper option — but it only works if it's arranged in advance, since bridging lenders need time to underwrite and complete, just like a standard mortgage.

It's worth stressing that bridging is a stopgap, not a substitute for having your chain properly aligned. Rates are materially higher than even a higher-risk mortgage product, and the loan needs a clear, realistic exit — in this case, the incoming sale proceeds — or it becomes an expensive ongoing liability.

Reducing Your Exposure Before You Exchange

• Don't agree to exchange until your mortgage offer is unconditional and you've checked its expiry date against your expected completion date, with margin for slippage.
• If your own sale is part of the chain, only exchange on your purchase once you're confident the sale below you is genuinely ready to exchange simultaneously.
• Ask your solicitor whether a 5% deposit is achievable if the full 10% would leave you financially exposed beyond what you could comfortably lose.
• Have a bridging contingency conversation with your broker in advance if there's any realistic chance your funds could be delayed past the fixed completion date — arranging it after the problem appears is often too late.
• Read the contract's special conditions carefully; some purchases (particularly new-build) include clauses that increase the buyer's exposure beyond the standard position.

Run your numbers through the Stamp Duty Calculator alongside the Mortgage Calculator before you exchange, so the total cash you need on completion day — deposit, SDLT, fees and mortgage advance — is confirmed well ahead of the date you're about to commit to.