Example result based on the prefilled values.
LISA Contributions Modelled
£20,000.00
Government Bonus
£5,000.00
Projected Balance
£25,000.00
Above Annual LISA Limit
£0.00
Continue your plan
Useful next calculations
Rates & sourcescurrent rules
Lifetime ISA contribution and government-bonus rules. The projected return, if any, is entered by you and is not a rate forecast.
Source: GOV.UK — Lifetime ISA — source checked for current rules.
When to use this calculator
- Before comparing lenders, brokers, or repayment options.
- When you want to test how a different deposit, rate, or term changes affordability.
- When you need a quick estimate before using a formal quote or agreement in principle.
- When you are stress-testing your budget against a potential rate rise to see the impact on monthly payments.
- When you want to understand the full cost of borrowing — not just the monthly figure — before you commit.
A realistic UK planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Planned LISA contribution each tax year (£)
£250 per month
Contribution horizon (years)
£250 per month
Current LISA balance (£, optional)
£1,400
Assumed annual return (%)
0
After entering these figures, review lisa contributions modelled, government bonus and projected balance together rather than in isolation — each metric tells a different part of the story. Then rerun the tool with one input adjusted to see which variable has the biggest effect on all three outputs before you settle on a plan.
How to read your results
LISA Contributions Modelled
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Government Bonus
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Projected Balance
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Above Annual LISA Limit
Use this metric to compare scenarios side by side and understand how changes in the key inputs drive the final outcome. If the figure surprises you, isolate one variable at a time and rerun the calculation to identify which assumption is responsible.
Method & assumptionsAuthoritative sources
This UK-only planner applies the published 25% Lifetime ISA government bonus to the first £4,000 entered for each modelled tax year. It can also apply an annual return you choose, but that return is only an assumption: investments can fall as well as rise and provider charges are not modelled.
It does not decide whether you can open, contribute to, use or withdraw from a Lifetime ISA. GOV.UK sets conditions including opening the account before age 40, contribution and bonus eligibility until age 50, a £450,000 first-home limit and a 12-month holding period for a qualifying first-home purchase. Check the current rules, your provider and a conveyancer or regulated adviser where appropriate.
Official references
Common mistakes
- !Mixing up loan amount and property value, which can distort affordability and LTV.
- !Using a headline rate but forgetting fees, insurance, taxes, or repayment type.
- !Testing only one term length instead of comparing the payment and total cost together.
- !Forgetting that a repayment mortgage and an interest-only mortgage produce very different monthly figures and total costs.
- !Not accounting for the impact of a rate revert after an introductory fixed period ends, which can sharply increase payments.
What to do next
- Run a second scenario with a higher rate or shorter term so you can see the downside clearly.
- Compare the result with an affordability or overpayment calculator before applying.
- Use the related guides below to understand trade-offs before you request live quotes.
- Note down the monthly payment and total interest for your two or three strongest scenarios so you have a clear comparison ready when you speak to a broker.
- Check whether making a modest overpayment each month would reduce total interest significantly — run the overpayment calculator next to find out.
Frequently asked
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