How does the 25% LISA bonus actually work?

For every £4 you pay into a Lifetime ISA, the government adds £1: a 25% top-up, paid monthly rather than at the end of the tax year (HMRC, 2026). You can pay in up to £4,000 in any tax year, which means the maximum bonus available in a single year is £1,000. There's no requirement to pay in a lump sum; monthly contributions of a few hundred pounds attract exactly the same 25% uplift as one big deposit in March.

Save the full £4,000 in a tax year and HMRC adds £1,000, taking your balance for that year to £5,000 before any interest or investment growth is added.

So the bonus is best understood as a guaranteed 25% return on your own money before a single penny of interest is earned. That's exactly why maximising your annual contribution each year is where the real value sits.

What happens if you max out your £4,000 allowance every year?

The bonus compounds in the sense that it arrives every year you contribute, not just once. Someone who pays in the full £4,000 annually for four years puts in £16,000 of their own money and receives £4,000 in bonuses, for a floor total of £20,000, before any interest on a cash LISA or growth on a stocks and shares LISA is added. That's what our calculator shows with the growth rate left at 0%: a floor, not a forecast. Enter your account's actual interest or growth rate above and the calculator estimates the compounding on top: at a steady 3% a year, that same four-year example grows to roughly £21,546, an extra £1,546 on top of contributions and bonus. Real returns are never guaranteed and will vary year to year, so treat any growth figure as an estimate rather than a promise.

Four-year worked example

£4,000 x 4 years = £16,000 contributed. 25% government bonus = £1,000 a year x 4 = £4,000. Grand total = £20,000 at 0% growth, or roughly £21,546 at a steady 3% annual growth rate.

So if you're weighing up whether to open a Lifetime ISA now versus in a year's time, every year you delay is a full £1,000 of bonus you can't get back; there's no catching up on missed allowance.

Why the £450,000 property price limit is a cliff-edge, not a taper

To use your LISA funds towards a first home, the purchase price must be £450,000 or under. There's no sliding scale here: go £1 over that threshold and you lose the ability to use the LISA for that purchase penalty-free. The whole scheme effectively switches off for that transaction. That's a meaningfully different design from, say, Stamp Duty, where each band only taxes the portion above the threshold. The calculator above checks this automatically against the property price you enter, showing whether you're within the limit or over it as you type. Worth also checking exactly what you'd owe on a given purchase price with our Stamp Duty calculator once you know roughly where you're likely to buy.

The £450,000 cap has not moved since the Lifetime ISA launched in April 2017. Average UK first-time buyer prices have risen substantially over the same period (ONS, 2026), which means the real-terms bite of that fixed limit has grown, particularly for buyers in London and the South East, where a perfectly ordinary flat can now sit uncomfortably close to the ceiling.

So if you're saving in a higher-cost area, run your numbers against the current asking prices for the postcode you actually want, not the postcode you could afford five years ago. The £450,000 limit hasn't kept pace with the market, and it won't necessarily wait for you either.

What does the early withdrawal penalty really cost you?

This is the part people misunderstand most often. If you withdraw LISA funds for anything other than a first property purchase, or before age 60, HMRC applies a 25% withdrawal charge, but that 25% is calculated on the whole amount withdrawn, including the bonus, not just on the bonus itself.

Take the £5,000 example from earlier: £4,000 of your own contributions plus a £1,000 bonus. Withdraw it early and the 25% penalty applies to the full £5,000, which is £1,250. You don't just lose the £1,000 bonus: you also lose £250 of your own original money on top of it. Contribute £4,000, get charged £1,250 to get it back out, and you're left with £3,750: a real loss, not a wash.

So a Lifetime ISA should only hold money you're genuinely confident you'll use for a first home under £450,000, or won't need again until age 60. Treating it as a flexible emergency fund is the single most expensive mistake this scheme allows you to make.

What this means for you

If you're a first-time buyer with a clear property price in mind and reasonable confidence you'll buy within the next few years, the maths points toward maxing out the £4,000 allowance every year you can afford to, since that bonus doesn't roll over or get topped up retrospectively. Most people who run these numbers end up treating the LISA as the core of their deposit strategy rather than a side pot, precisely because nothing else in mainstream saving offers a guaranteed 25% uplift. If you're not yet sure the maths stacks up against renting where you are, our rent vs buy calculator is a useful next stop, and once you've got a savings timeline in mind, our affordability calculator will tell you what mortgage that deposit is actually likely to support.