Deposit & Lifetime ISA (LISA) Savings Calculator

Why the LISA math needs a month-by-month simulation, not a quick estimate

A lot of "LISA calculator" content online simply multiplies your annual contribution by 25% and calls it done. That works fine as long as you never contribute more than £4,000 in a tax year — but the moment a monthly LISA contribution, projected out over 12 months, would exceed that cap, a simple multiplication overstates the real bonus you'll actually receive. This calculator instead simulates your savings month by month: it tracks how much LISA contribution room you have left in the current tax year, applies the 25% bonus only to the portion that's actually within the £4,000 cap, and resets that room each 6 April, using the month you tell it your saving starts in. If your plan would exceed the cap, the results panel tells you directly, rather than quietly showing an inflated bonus figure.

Two numbers that are easy to mix up: your deposit target and the £450,000 price cap

The Lifetime ISA can only be used penalty-free towards a first home priced at £450,000 or under — this is a cap on the property's purchase price, not on the size of the deposit you're saving. This calculator's "target deposit amount" is simply the cash figure you're aiming to accumulate; in the plain amount mode it cannot check that figure against a property price, because it has no way of knowing what property you'll eventually buy. In the price-and-percentage mode it does warn you when the price is over the limit. If you're saving towards a home that might end up priced above £450,000, factor that in separately — your LISA savings would still exist and could still be withdrawn (subject to the usual conditions), but the purchase itself wouldn't qualify for a penalty-free LISA withdrawal on a property over that limit.

Is the Lifetime ISA being replaced? What the 2026 consultation says

HM Treasury consulted on a new first-time-buyer ISA to be offered in place of the Lifetime ISA. According to the GOV.UK consultation page, it ran from 22 June to 18 August 2026 and is now closed, with the government analysing responses. The design discussed would pay the government bonus when you withdraw to buy a first home rather than as you save, and would not carry the LISA's 25% charge for withdrawing for the wrong reason. Existing LISA holders have been reported as able to keep paying in under today's rules. We have not seen a published outcome, a start date or a confirmed property price limit, so none of that is modelled: this calculator uses the LISA exactly as it works today. If your plan runs several years, check the consultation page for the outcome before relying on any rule.

How much deposit do you need? The cash at common percentages

There is no single required deposit: each lender sets its own minimum and prices mortgages by how large your deposit is compared with the price, so ask a broker what applies to you. For the cash involved, this is plain arithmetic: the deposit at 5%, 10%, 15% and 20% of common prices. Put any figure into the calculator above to see how long it takes.

Remember the cash on completion also includes stamp duty in England and Northern Ireland, due within 14 days of completion: see the stamp duty calculator. For Shared Ownership, GOV.UK says the deposit is usually 5% to 10% of the share you are buying rather than of the full price, which can make the cash needed far smaller. How the mortgage then looks is in the NHS Mortgage Calculator and the mortgage repayment calculator.

What this calculator does and doesn't do

• ✓ Calculates exactly how many months it'll take to reach your target deposit, given your current savings, monthly savings amount, and how much of that goes into a LISA.
• ✓ Applies the LISA's 25% government bonus and £4,000/year contribution cap correctly, month by month — not as a simplified annual estimate.
• ✓ Flags when your modelled LISA contributions would exceed the annual cap in a full year, so the real bonus doesn't get silently overstated.
• ✓ Warns when a price you enter in the price-and-percentage mode is over the £450,000 LISA limit, and when the 12-month rule would apply. In the plain amount mode it cannot know your property price, so keep that limit in mind yourself.
• ✓ Does not model the 25% early-withdrawal penalty in the calculation itself — this tool is for people saving towards a purchase, not withdrawing early — but the risk is explained clearly above and in the results.
• ✓ Optionally adds interest at a yearly rate you enter. It never assumes a rate, and it does not account for tax on interest outside an ISA, house price inflation or any future change to LISA rules.

LISA vs NHS Credit Union payroll saving: two genuinely different ways to build this same deposit

A Lifetime ISA isn't the only structured way NHS staff build a deposit — FrontlinePay's own NHS Credit Union Payroll Savings guide covers a genuinely different mechanism: an amount you choose, deducted automatically from your salary each pay period (where your employer holds a live partnership with NHS Credit Union — it currently isn't every trust or health board) and paid into your own credit union savings account. It's worth understanding both side by side, honestly, rather than assuming a LISA is automatically the "correct" choice just because it comes with a government bonus.

Neither is objectively "better" — this is a genuinely personal choice that depends on how confident you are about buying a first home under the price cap within a reasonable timeframe, and how much you value being able to access the money for something else if your circumstances change. Someone who's certain they're buying their first home in the next few years, and won't need the money for anything else, is giving up a real 25% bonus by not using a LISA. Someone who isn't sure yet whether or when they'll buy, who's already used their LISA allowance for the year, or who simply wants an accessible fund with zero lock-in risk, may reasonably prefer payroll saving instead — or a mix of both, splitting a monthly savings amount between the two. Read the full mechanics, and the important caveat that this isn't a universal NHS benefit, in the NHS Credit Union Payroll Savings guide, part of FrontlinePay's wider NHS Savings & Salary Sacrifice hub.

Worked example: a newly-qualified Band 5 nurse saving for a first deposit

To make this concrete, here's how the numbers play out for a newly-qualified NHS employee on Band 5, point 1 (England/Wales/NI Agenda for Change pay), the entry point most nurses, paramedics, physiotherapists and radiographers start on straight after qualifying — exactly the first-time-buyer segment FrontlinePay's own Nurses' and Healthcare Assistants' mortgage guides identify as typically having the least savings to work with. These figures are pulled live from the same real Agenda for Change pay data and take-home pay engine used across the rest of this site — not hand-typed — assuming no High Cost Area Supplement, standard 2015 NHS Pension Scheme membership, and no student loan.

• Band 5, point 1 basic salary (full time): £32,073/year
• Estimated take-home pay: £2,040/month
• Saving an illustrative 10% of take-home pay: £204/month
• Example target deposit: £15,000

On these assumptions, using a LISA gets this same saver to the same £15,000 target roughly 15 months sooner, purely because of the £3,009 government bonus — not because they saved any more of their own money. This is one illustrative example on one set of assumptions, not a prediction of your own timeline: your own band, point, location, pension status, student loan and realistic monthly savings amount will very likely be different. Load this exact example into the calculator above to see it directly, then adjust every figure to your own circumstances — or check your real take-home pay first on the NHS Pay Calculator.

How this fits with FrontlinePay's other mortgage tools

Saving the deposit is naturally the first step before working out how much you could borrow on top of it. Once you have a deposit figure and rough timeline from this calculator, take it to the NHS Mortgage & Borrowing Calculator, which uses your real NHS salary (sole or joint) to estimate a realistic borrowing range — giving you the full picture of deposit plus borrowing power together. Deposit-building is a theme across every profession guide on the NHS Mortgages hub, with routes like the LISA, Shared Ownership and the First Homes scheme covered in the context of each specific role — nurses, doctors, midwives, paramedics, pharmacists, allied health professionals, healthcare assistants, and admin & estates staff.

Method and sources

• • LISA rules: GOV.UK Lifetime ISA pages, checked 6 October 2026 (£4,000 a year, 25% bonus up to £1,000, first payment before 40, pay in to 50, first home up to £450,000 with a mortgage at least 12 months after the first payment, 25% charge on unauthorised withdrawals).
• • The bonus is modelled as arriving with each monthly contribution; in practice it is paid by the government on a monthly basis, which this simplification matches closely.
• • The £4,000 limit resets on 6 April, using the start month you choose. Ordinary savings are modelled with no bonus and optional interest at the rate you enter.
• • Take-home pay in the worked example: our 2026/27 Agenda for Change data and shared tax, National Insurance and NHS Pension engine.

See our editorial policy and corrections policy. This is not financial advice.