The short answer
Many first-time buyer mortgages require at least a 5% deposit, although the deals available depend on the property and your circumstances. On a £250,000 home, 5% is £12,500 and 10% is £25,000. The mortgage covers the rest, subject to valuation and affordability checks.
A deposit is not your complete buying fund. Keep separate money for tax where applicable, mortgage fees, conveyancing, searches, a survey, moving and the first repairs. Using every pound for the deposit can leave an otherwise affordable purchase dangerously fragile.
Understand loan-to-value
Loan-to-value, or LTV, is the mortgage as a percentage of the property's value. A £225,000 mortgage on a £250,000 home is 90% LTV. A lower LTV usually gives the lender more protection and can unlock a wider choice of deals, but rates and bands vary by lender.
The value used by the lender may be lower than your agreed price. If a lender values the home at £240,000 rather than £250,000, it may reduce the amount it will lend. Decide before offering how you would respond to a down valuation instead of assuming family savings will fill any gap.
When a bigger deposit helps—and when it does not
Moving into a lower LTV band can reduce the rate or increase the number of products available. Ask for comparisons at several deposit sizes so you can see whether an extra pound of deposit creates a meaningful saving.
Do not cross an LTV threshold at the cost of having no emergency cash. A boiler, service-charge demand or urgent repair does not wait for your savings to recover. The right deposit is the one that produces a sustainable mortgage and leaves the rest of the purchase funded.
Gifted deposits and source of funds
If family is helping, tell your broker, lender and conveyancer at the beginning. The lender may require a gifted-deposit letter confirming whether the money is a gift, whether it must be repaid and whether the giver expects any interest in the property.
Your conveyancer must verify where purchase money came from. Keep bank statements showing the savings build-up and transfer trail. Large unexplained cash movements close to exchange can create avoidable delay.
Set a target you can actually use
- Calculate 5%, 10% and 15% deposits for your likely price range.
- Get mortgage illustrations at the corresponding LTV bands.
- Create a separate buying-cost pot and an after-completion emergency fund.
- Open and fund a Lifetime ISA early if it suits you; the first-home withdrawal rules include a 12-month clock.
Sources and further reading
- MoneyHelper: First-time home buyer guide
- MoneyHelper: Mortgage deposit guide
- MoneyHelper: Mortgage in principle explained
Mortgage availability depends on the lender, property and borrower. This article is general information and was last checked on 11 August 2026.