On a £300,000 property, a £15,000 deposit and a £60,000 deposit look like they belong to different financial worlds — one is a stretch that many first-time buyers manage after years of saving, the other requires considerably more time, income or help.
But the mortgage doesn’t improve in a straight line as the deposit grows.
Some of that extra money can unlock a genuinely better rate. Some simply reduces the amount borrowed without changing the pricing band at all. And sometimes the most valuable few thousand pounds are the last few needed to cross a lender’s loan-to-value threshold, rather than the much larger amount already saved.
Knowing where those thresholds sit — not as fixed rules, because lenders and mortgage pricing change constantly, but as part of the way the market works — is what separates a deposit strategy from simply saving for as long as possible and assuming every extra pound must produce an equally better mortgage.
What loan-to-value actually means
Loan-to-value, or LTV, is the mortgage expressed as a percentage of the property’s value.
On that same £300,000 property, a £15,000 deposit means borrowing £285,000, giving a 95% LTV. A £30,000 deposit means borrowing £270,000, or 90% LTV. Put down £60,000 and the mortgage falls to £240,000, or 80% LTV.
The lower the LTV, the more of the purchase price the buyer is funding themselves and the greater the lender’s cushion if property values fall. That is why lower-LTV mortgages usually come with a wider choice of products and, in general, lower interest rates.
MoneyHelper’s guidance on mortgage deposits makes the broad relationship clear: a larger deposit creates a lower LTV and will usually improve the mortgage deal available, with the most competitive rates typically appearing at substantially lower LTVs.
The important word is usually. The improvement doesn’t arrive smoothly with every additional pound.
Where the rate actually jumps
Mortgage pricing works in bands.
A lender might offer one range up to 95% LTV, another up to 90%, another at 85%, with further pricing points lower down. The exact thresholds vary between lenders, and not every provider uses precisely the same bands, which is why “save 20%” is not a universal mortgage rule.
A 20% deposit gives you an 80% LTV. That is useful in itself because you’re borrowing less, but it does not automatically mean every lender will suddenly offer a materially better rate at exactly 80%. One lender may have an important pricing point there; another may have its next notable tier at 75%.
The practical target is therefore not a particular deposit percentage in isolation. It is the next useful LTV band among the mortgages you could realistically obtain.
The current market shows why this matters.
On 12 September 2026, Rightmove’s mortgage-rate tracker put average two-year fixed homebuyer rates at 5.78% at 95% LTV, 5.33% at 90%, 5.12% at 85%, 5.05% at 75% and 4.72% at 60%. Those averages were based on products with a fee of around £999 and are a snapshot, not rates every borrower will qualify for or a guide to where pricing will sit later.
But the shape is revealing.
In that snapshot, moving from 95% to 90% LTV reduced the average rate by about 0.45 percentage points. Moving from 90% to 85% produced a smaller 0.21-point improvement, while the difference between the published 85% and 75% averages was only 0.07 points despite requiring much more equity.
There was another meaningful improvement between 75% and 60%, but reaching it requires an additional 15% of the property’s value.
So there isn’t one point after which a deposit “stops helping”. The returns are lumpy.
That is precisely why the next band matters more than a generic target such as 10%, 15% or 20%.
It is also why the rate alone isn’t enough. Crossing a threshold may unlock a cheaper product, but that product may carry a different arrangement fee or incentive. The useful comparison is between the actual mortgages available on either side of the threshold, including their fees, rather than assuming the product with the lower percentage rate must automatically be cheaper.
Why the last few thousand pounds can matter disproportionately
The £300,000 example makes the threshold effect clearer.
Suppose a buyer has saved a 9% deposit — £27,000. They need to borrow £273,000.
To illustrate the principle rather than reproduce a lender’s actual offer, price that mortgage using the 5.78% average shown above for 95% LTV products. Over 30 years, the monthly repayment would be about £1,598.
The buyer then saves another £3,000, taking the deposit to £30,000 and the mortgage down to £270,000 — exactly 90% LTV.
Using the corresponding 5.33% average rate, the monthly repayment falls to about £1,504.
That’s approximately £94 a month less.
The interesting part is where that saving comes from.
If the rate had remained at 5.78%, simply reducing the mortgage from £273,000 to £270,000 would have saved only about £18 a month.
The remaining £76 or so of the illustrative monthly reduction comes from the lower interest rate being applied across the much larger £270,000 balance.
That is why the final £3,000 needed to cross an LTV threshold can sometimes have a disproportionate effect. It isn’t merely reducing the mortgage by £3,000. It may also change the price charged on almost all of the money still being borrowed.
Actual lender thresholds, rates, fees and eligibility will differ, so this should never be read as a promise that a 10% deposit will produce exactly this saving.
But it shows why the right question isn’t simply “how much more can I save?”
It’s “what happens to the mortgage if I save the next £3,000?”
Sometimes the purchase price can move you across the line too
The deposit isn’t the only number in the LTV calculation.
The price being paid matters just as much.
Imagine a buyer has £30,000 available and agrees to pay £305,000 for a property. They need a £275,000 mortgage, putting the LTV at a little over 90%.
If negotiation brought the purchase price down to £300,000 while the buyer kept the same £30,000 deposit, the required mortgage would fall to £270,000 — exactly 90% LTV.
The buyer has not saved another pound.
They have paid £5,000 less for the property and, depending on the lender’s product bands and valuation, may also have moved into a more favourable mortgage tier.
That doesn’t mean buyers should negotiate around an arbitrary mortgage percentage rather than what the property is actually worth. Nor does crossing 90% guarantee a better product.
It does mean that somebody sitting just above an important LTV boundary should understand both sides of the equation before deciding how much more deposit they need.
Where the returns start to diminish
This is the part worth understanding before deciding that the biggest possible deposit must automatically be the best use of every available pound.
Moving from 5% towards 10% can make a large difference because it reduces both the amount borrowed and, in many market conditions, the premium attached to very high-LTV lending.
Moving from 10% towards 15% or 20% can still improve the choice and pricing available, but the value becomes increasingly dependent on the lender and the particular pricing bands on offer at the time.
Someone with a 7% deposit pushing towards 10% may therefore be chasing a meaningful mortgage improvement. Someone who already has 20% should not simply assume that another 5% or 10% will produce a comparable reward.
The useful exercise is to compare the actual mortgages available at the current deposit and at the next one or two realistic LTV thresholds.
If an extra £10,000 saves only a small amount on the mortgage but would leave the buyer with no emergency reserve, the lower rate may not represent the stronger overall financial position.
There is another complication buyers can miss: the lender has its own view of the property’s value.
A £30,000 deposit against an agreed £300,000 price appears to produce a perfect 90% LTV. But the lender will normally arrange or obtain a valuation, and the result can affect the final mortgage offer. MoneyHelper’s mortgage application guidance notes that a lender may reduce the amount it is prepared to lend where the property is valued below the agreed price.
That matters particularly when the deal is sitting right on an LTV threshold.
A buyer should not assume that calculating a 10% deposit against the agreed purchase price guarantees the lender will also treat the mortgage as exactly 90% LTV.
The mortgage/deposit question, kept separate from house prices
Whether to buy now with a smaller deposit or wait to build a larger one is not the same question as whether house prices will rise or fall while you wait.
Those two decisions are often mixed together, but they involve different risks.
From the mortgage side alone, a smaller deposit generally means a larger loan, higher LTV and potentially a higher rate. A larger deposit means borrowing less and may open better mortgage pricing.
Waiting also has a cost.
A renter continues paying rent while saving. The property they eventually want may cost more or less. Mortgage rates themselves can change. The next LTV band may become more or less valuable as lenders reprice.
None of that can be solved by assuming house prices will conveniently remain still while the deposit grows.
The useful question for this article is narrower: what mortgage improvement does the extra deposit actually buy at today’s numbers?
If the answer is substantial, waiting may deserve serious consideration. If the answer is marginal, the decision depends much more heavily on the rest of the buyer’s circumstances.
The case for keeping cash back
It is tempting to treat “biggest possible deposit” as an automatically sensible goal.
It isn’t.
Buying a home requires cash beyond the deposit: legal and conveyancing costs, surveys, removals, mortgage fees where applicable, insurance and whatever the property itself requires shortly after completion. MoneyHelper’s guide to buying and moving costs is a useful reminder of how quickly those costs accumulate.
Property transaction taxes need to be allowed for as well, and this is one area where UK jurisdiction matters.
In England and Northern Ireland, eligible first-time buyers currently pay no Stamp Duty Land Tax on the first £300,000 of a qualifying purchase costing no more than £500,000, and 5% on the portion between £300,000 and £500,000. The current thresholds are set out in the government’s First-Time Buyers’ Relief guidance. Scotland uses Land and Buildings Transaction Tax and Wales uses Land Transaction Tax instead.
The bigger financial point is the same whichever part of the UK you’re buying in.
A household that puts every available pound into reaching the next deposit band and completes with virtually nothing left has made the mortgage cheaper while potentially making the household more fragile.
Imagine the choice is between using the final £5,000 to improve the deposit or keeping it accessible after completion. If that £5,000 crosses an important LTV boundary and substantially improves the mortgage, using it may make sense. If it barely changes the products available, keeping it outside the property may be far more valuable the first time a boiler, appliance, roof or income problem appears.
A bigger deposit and a stronger financial position are not always exactly the same thing.
Negative equity: a real risk, not an inevitable one
Higher-LTV borrowing leaves less protection against a fall in the property’s value.
On a £300,000 purchase with a 5% deposit, the buyer begins with £15,000 of equity. Before allowing for mortgage repayments, a 5% fall in the property’s value would take it to £285,000 — effectively wiping out that initial equity.
With a 10% deposit, the same 5% fall would still leave a larger cushion.
That is why high-LTV borrowing deserves more thought if the buyer may need to sell again relatively soon.
MoneyHelper’s negative-equity guidance explains why the problem becomes particularly important when somebody needs to move or obtain another mortgage deal: if the property is worth less than the outstanding mortgage, both can become difficult.
This doesn’t mean a 95% mortgage inevitably leads to negative equity, or that taking one is inherently imprudent.
On a repayment mortgage, each capital repayment gradually reduces the amount owed. If the property’s value remains unchanged, that alone builds equity over time.
The risk is simply greater at the beginning because there is less margin between the property value and the debt.
For somebody intending to remain in the home for years, that risk has a different significance from somebody who already knows another move may be needed relatively soon.
The Mortgage Guarantee Scheme doesn’t make a 5% deposit automatically better
There is now a permanent government-backed route supporting the availability of high-LTV mortgages.
The Mortgage Guarantee Scheme introduced in July 2025 supports participating lenders offering eligible mortgages between 91% and 95% LTV, allowing qualifying first-time buyers and home movers across the UK to buy with a deposit as small as 5%.
One distinction matters.
The government guarantee protects the lender against part of its potential loss. It does not pay part of the buyer’s mortgage, protect the buyer from negative equity or guarantee that a scheme-backed mortgage will be the cheapest 95% deal available.
The borrower still owes the mortgage in full and still has to satisfy the lender’s affordability and credit criteria.
That makes the scheme useful for availability rather than a reason to stop comparing.
A buyer with a 5% deposit should still compare the rates, fees and conditions actually available to them — including ordinary high-LTV mortgages where available — rather than assuming a government-backed product must automatically be the best option.
Other home-buying support varies across England, Scotland, Wales and Northern Ireland, so eligibility should be checked against the current scheme rules in the relevant nation rather than relying on an old list of schemes.
Gifted deposits need to be evidenced properly
Where some or all of the deposit comes from family or somebody else, the mortgage application needs to make that clear.
MoneyHelper’s mortgage application guidance includes proof of deposit among the documents a lender may request, including evidence or forms where money has been gifted.
Exact requirements vary between lenders and conveyancers, but it is common to be asked to show where the money came from and whether it is a genuine gift rather than borrowing that needs to be repaid.
That distinction matters because money described as a gift but actually repayable is another financial commitment and can affect affordability.
For buyers receiving family help specifically to reach an LTV threshold, it is worth sorting out that paperwork early rather than discovering late in the application that the lender or conveyancer needs further evidence.
So is 5%, 10% or 20% the right deposit?
There isn’t a universal percentage.
But if a broad pattern can be drawn, moving from a 5% deposit towards 10% is often one of the more valuable steps, because very high-LTV mortgages can carry noticeably higher pricing and a narrower choice of products.
Moving from 10% towards 15% or 20% can still help — by reducing the mortgage, increasing equity and sometimes opening another pricing band — but the benefit becomes increasingly dependent on the lender and the products available at the time.
Twenty per cent is not a magic number.
Nor is 10%.
The number that matters is the next deposit level that actually changes something meaningful: the rate, the product choice, the loan amount or the household’s resilience.
Strip away the percentages and the decision is really about allocating a finite amount of cash.
Some goes into the property, reducing the mortgage and potentially opening a cheaper LTV band.
Some needs to pay the costs of buying.
And some may be more valuable remaining outside the property altogether as a reserve for the ordinary unpredictability of homeownership.
That is why “How big a deposit can I possibly make?” is not quite the right question.
The better question is: what does the next chunk of deposit actually buy me?
If another £3,000 moves the mortgage into a meaningfully cheaper band, it may be some of the most productive money in the whole deposit.
If another £15,000 leaves the available mortgage virtually unchanged but empties the savings account, its value is much less obvious.
The percentage itself is not the prize.
The aim is to reach the most useful mortgage position you reasonably can without making the rest of your financial position weaker to get there.
This article provides general information about mortgage deposits and is not personalised mortgage, financial or investment advice. Mortgage rates, LTV bands, valuations, fees and scheme eligibility change and depend on individual circumstances and lender criteria. Worked examples are illustrative only, and current rate examples are a snapshot rather than a forecast. Before deciding how much cash to commit to a deposit, compare the actual mortgage products available to you and, where appropriate, seek advice from an FCA-authorised mortgage adviser.
