UK Deposit Unlock Calculator
Calculate monthly payments with a 5% deposit on a new build property using the Deposit Unlock scheme. Compare against 10%, 15%, and 20% deposit scenarios, understand how the insurance-backed scheme works versus Help to Buy, check negative equity risk if prices fall, and see how quickly you can overpay to reach a better 90% LTV remortgage rate.
Deposit Unlock is an industry-led mortgage indemnity scheme that allows buyers to purchase new build homes with just a 5% deposit. Unlike Help to Buy, it is not a government scheme and does not involve an equity loan.
A 95% LTV mortgage carries a rate premium compared to 90% LTV. The rate premium reflects the higher risk to the lender. Here is the full cost of that premium over your mortgage term.
| Deposit | LTV | Deposit Amount | Est. Rate | Monthly Payment | Total Cost (25yr) | vs 5% Deposit |
|---|---|---|---|---|---|---|
| 5% | 95% | £14,000 | 5.40% | £1,618/mo | £485,288 | — |
| 10% | 90% | £28,000 | 5.05% | £1,481/mo | £444,155 | -£41,132 |
| 15% | 85% | £42,000 | 4.85% | £1,371/mo | £411,181 | -£74,106 |
| 20% | 80% | £56,000 | 4.65% | £1,264/mo | £379,264 | -£106,024 |
How to Use This UK Deposit Unlock Calculator
Enter the new build property price, your interest rate with a 5% deposit, and mortgage term. The calculator instantly compares the monthly payment and total cost at 5%, 10%, 15%, and 20% deposit levels, showing the full premium you pay for using Deposit Unlock versus saving a larger deposit.
What is Deposit Unlock?
Deposit Unlock is an industry-led mortgage indemnity scheme that allows buyers to purchase new build homes with a 5% deposit and a standard repayment mortgage. The housebuilder pays an insurance premium to a participating insurer, which then protects the lender against losses — enabling the lender to accept a 95% LTV loan on a new build property. Unlike Help to Buy, there is no government equity loan and you own 100% of your property from day one.
How Deposit Unlock Works
5% Deposit (buyer): £14,000
Mortgage: £266,000 (95% LTV)
Builder pays: ~0.9% indemnity insurance premium = ~£2,520
Insurer covers lender if buyer defaults at 95% LTV
Buyer owns 100% — no equity loan, no deferred cost
Rate vs 90% LTV: typically +0.3% to +0.5% higher
The scheme is entirely transparent to the buyer in terms of ownership — you take out a normal repayment mortgage and build equity through monthly payments and property appreciation. The only cost to you is the slightly higher mortgage rate associated with 95% LTV versus 90% LTV.
Deposit Unlock vs Help to Buy
Help to Buy (England) closed to new applicants in October 2022. Deposit Unlock is the main 5% deposit route for new builds from 2023 onwards. Key differences:
- No equity loan: You are not taking a government loan that must be repaid on sale. Your full property gain belongs to you.
- Not first-time buyers only: Any eligible buyer can use Deposit Unlock, including home movers. Help to Buy was restricted to first-time buyers in its final iteration.
- No deferred costs: There is no loan fee starting after 5 years, unlike Help to Buy's 1.75% fee rising with inflation.
- Builder-funded: The insurance premium is paid by the housebuilder, not the government or the buyer.
Example: Buying a Barratt Home in Birmingham
Emma buys her first home with a 5% deposit
Emma has saved £14,000 and wants to buy a new Barratt Homes property priced at £280,000 in Birmingham. Barratt participates in Deposit Unlock.
| Property Price | £280,000 |
| Deposit (5%) | £14,000 |
| Mortgage | £266,000 at 5.4% (95% LTV) |
| Monthly Payment (25yr) | £1,628/month |
| 10% Deposit Alternative | £1,572/month at 5.05% — saves £56/mo |
| Total Extra Cost (5% vs 10%) | ~£16,800 over 25 years |
| Negative equity risk | Any price fall above 5% = negative equity |
| Time to reach 90% LTV (no overpay) | ~4 years 6 months |
Emma gets into her home 18 months sooner than if she saved for a 10% deposit. The trade-off is around £56 more per month and total extra cost of £16,800 over the full term at her current rate.