How Your Deposit Size Affects Mortgage Borrowing

Most people understand that a bigger deposit means borrowing less. That part is straightforward. What most people do not realise is that certain deposit thresholds unlock higher income multiples from lenders — meaning you can actually borrow more in absolute terms despite putting more money down. The result is that your total purchasing power can jump significantly when you cross specific loan-to-value boundaries.

This guide explains where those step changes happen, why they exist, and how to work out whether saving a little longer could dramatically increase the property you can afford.

The deposit thresholds that matter

Lenders do not treat deposit size as a smooth scale. Instead, they work in bands — and your borrowing terms can change sharply when you cross from one band to the next. Here are the four thresholds that matter most.

5% deposit (95% LTV)

This is the minimum most lenders will accept. At 95% LTV your options are limited: fewer lenders participate at this level, interest rates are at their highest, and income multiples are typically capped at 4x to 4.5x. Mandatory affordability stress testing at the higher rate reduces your maximum borrowing further. For many buyers, this is the entry point — but it comes with the most restrictive terms.

10% deposit (90% LTV)

Crossing from 5% to 10% deposit opens up nearly all mainstream lenders. You will see noticeably better interest rates, which improves your stress test result. However, income multiples for most lenders remain in the standard 4x to 4.5x range at this level. The main benefit is choice: more lenders competing for your business means better deals overall.

15% deposit (85% LTV)

This is often where the biggest step change occurs. At 85% LTV, some lenders move from offering 4.5x income to 5x or even 5.5x income. Combined with better interest rates reducing the stress test burden, this threshold is where your total purchasing power can actually increase despite the larger deposit. For buyers who can stretch from 10% to 15%, this is often the most impactful move they can make.

20-25% deposit (75-80% LTV)

At 75% LTV and below, you access the best rates available in the market and the maximum income multiples from most lenders. Some specialist lenders only operate at these lower LTV tiers, offering particularly generous terms for borrowers with substantial equity. If you can reach this level, you are in the strongest possible negotiating position.

Worked example: how £23,000 unlocks £38,900

Numbers make this clearer than words. Consider a buyer earning £40,000 per year looking at properties around £230,000.

This is not a rounding error. The buyer who saves an extra £23,000 does not just reduce their loan by that amount — reaching 85% LTV opens lenders' higher multiples and lower rates, so the budget grows by more than the deposit.

Which lenders increase at which thresholds

Not all lenders respond to deposit size in the same way. The variation between them is significant, and understanding the general patterns helps you target your saving strategy.

Building societies tend to be more generous at lower LTVs. Many mutuals offer their highest income multiples once you reach 85% or 80% LTV, and several have specific products designed for borrowers with larger deposits. If you can reach 15% or more, some building societies may offer higher income multiples than the big banks.

High street banks usually set their maximum income multiple by both your income and your loan-to-value, so a bigger deposit can unlock a higher multiple as well as a better rate. Halifax, for example, lends up to 5.5x at 75% LTV or below to applicants earning over £75,000, but 5x up to 85%, 4.75x up to 90% and 4.49x above 90%. Barclays, TSB and Virgin Money generally keep their enhanced multiples for loans at 85% LTV or below, and Santander, HSBC and NatWest cut their multiples above 90% LTV. On lower incomes (roughly under £40,000 to £50,000) several big banks stay at about 4.45x–4.49x whatever your deposit, so at those incomes the main gain is a better rate.

Specialist lenders may only appear at 75-80% LTV or below. These lenders can offer particularly attractive terms — sometimes 5.5x income or higher — but they require substantial equity before they will consider your application.

Because the landscape varies so much between lenders, it's worth comparing several. Our calculator checks 57 lenders so you can see where the step changes are for your specific income and deposit combination.

Should you wait and save more?

This is one of the most common questions buyers face, and the answer depends on your specific numbers. There are genuine trade-offs in both directions.

The case for saving longer: If you are close to a threshold — say you have 12% deposit and could reach 15% within six months — the step change in borrowing power may far outweigh the cost of waiting. As the worked example above shows, crossing from 95% to 85% LTV can add tens of thousands to your total budget.

The case for buying now: Property prices may rise while you save, eroding the benefit. If prices in your area are increasing by 5% per year, a £230,000 property becomes £241,500 in twelve months. Your larger deposit may simply be absorbed by the price increase rather than improving your LTV position.

Our deposit calculator shows how each extra 5% of deposit changes the price you could buy at, which can help you find the right balance for your situation.

It is also worth considering whether clearing existing debt might have a bigger impact than saving more deposit. Sometimes clearing £300 per month of car finance increases your borrowing power more than an extra £10,000 in deposit — because it directly improves your affordability ratio with every lender.

Government help with deposits

Several government-backed schemes can help you build a deposit faster or reduce the amount you need.

Lifetime ISA: Save up to £4,000 per year and receive a 25% government bonus of up to £1,000 annually. Over four years of maximum contributions, that is £4,000 of free money added to your deposit. The account must be open for at least 12 months before you can use it, and the property must cost £450,000 or less. The government plans to offer a new First Time Buyer ISA in place of the Lifetime ISA but hasn't set a launch date. Until it launches you can still open a LISA, and if you already have one you can keep paying into it under the current rules afterwards, though you can pay into only one of the two accounts in any tax year.

Shared Ownership: Buy between 10% and 75% of a property and pay rent on the remainder to a housing association. Because your mortgage is only on the share you purchase, the deposit required is dramatically lower. A 10% deposit on a 50% share of a £300,000 property is £15,000 rather than £30,000.

First Homes scheme: Offers homes in England to first-time buyers at a discount of at least 30% (councils may prioritise local key workers), for households earning up to £80,000 (£90,000 in London), with a price after discount of no more than £250,000 (£420,000 in London). The discount is locked to the property in perpetuity, meaning it is passed on when you sell. Since planning rules changed in December 2024, each council decides whether to deliver First Homes at all, and supply has been falling, so check with your council and see our First Homes guide.

Family support mortgages: Joint Borrower Sole Proprietor (JBSP) mortgages allow a parent or family member to support your application with their income without being on the property title. That can raise how much you can borrow, but it doesn't lower your loan-to-value: you still need the deposit the lender asks for. Guarantor mortgages work differently, with the family member's savings or property used as additional security, which can let you borrow with a smaller deposit. The family member is legally responsible for the whole mortgage (JBSP) or for your shortfall (guarantor), and their savings or home can be at risk. Lenders usually require them to take their own legal advice first.

The government has announced Your First Home, a new equity-loan scheme in England for first-time buyers of new-build homes, expected to support 2.5% deposits backed by a 20% government-backed equity loan. It isn't open yet: the details are due at the Budget on 28 October 2026, and no launch date has been set.

Frequently asked questions

Does a bigger deposit always mean more borrowing power?

Not just because the loan is smaller. Crossing certain loan-to-value thresholds — especially 85% LTV (15% deposit) — can unlock higher income multiples from lenders, sometimes jumping from 4.5x to 5.5x income, so your total purchasing power can actually increase rather than just reduce your loan size.

Which deposit threshold makes the biggest difference?

The 15% deposit (85% LTV) threshold typically delivers the largest step change, as some lenders raise income multiples from 4.5x to 5x or 5.5x at this level. In our worked example, an extra £23,000 of deposit unlocked £38,900 more total budget — £15,900 more than the extra savings.

Can government schemes help me reach a higher deposit threshold faster?

Yes. The Lifetime ISA adds a 25% government bonus (up to £1,000 a year) to deposit savings, Shared Ownership lowers the deposit needed by only requiring a deposit on the share you buy, and a guarantor mortgage can let a family member's savings or property stand in for part of the deposit. (JBSP adds a family member's income instead, which raises borrowing but doesn't lower the deposit you need.) Either way the family member takes on real liability, and their savings or home can be at risk. The government plans to offer a new First Time Buyer ISA in place of the Lifetime ISA but hasn't set a launch date. Until it launches you can still open a LISA, and if you already have one you can keep paying into it under the current rules afterwards, though you can pay into only one of the two accounts in any tax year.

See how your deposit changes your results

The impact of your deposit depends entirely on your income, your existing commitments, and which lenders are available at your specific LTV. Each lender has its own thresholds and criteria.

Mortgage Affordability checks your details against 57 UK lenders simultaneously, running them through each lender's affordability calculation (its own calculator where available, otherwise a model of its published criteria). Try running your figures at different deposit levels to see where the step changes occur for your situation. You may find that a relatively small increase in deposit crosses a threshold that transforms your results.

Last updated: October 2026