Help to Buy ISA — Calculate Your Government Bonus — UK 2026

ISA Calculator UK

Understanding Your Investment Returns

This calculator projects your returns using compound interest, where your earnings generate their own earnings over time. The power of compounding means that even small regular investments can grow into substantial wealth over long periods. For example, investing just Rs 5,000 per month at 12% expected returns for 25 years can grow to over Rs 1 crore — of which only Rs 15 lakh is your own money and Rs 85 lakh is compounding returns. The key factors that determine your final corpus are: the amount invested, the rate of return, the duration of investment, and the frequency of compounding.

Important Considerations

Past returns do not guarantee future performance, especially for market-linked instruments like mutual funds and equities. The returns shown are estimates based on the rate you enter. Equity investments carry market risk but have historically delivered 12-15% CAGR over 15+ year periods in India. Fixed income options like PPF (7.1%) and FD (6-7.5%) offer lower but more predictable returns. Diversifying across asset classes — equity, debt, gold, and real estate — reduces overall portfolio risk while optimizing returns for your risk tolerance.

HTB ISA Bonus Maths

The Help to Buy ISA pays a 25% government bonus on your closing balance when you buy a first home, subject to hard limits. The minimum bonus is £400, which requires at least £1,600 saved; the maximum is £3,000, requiring £12,000. Deposits are capped at £1,200 in the first month, then £200 per calendar month — so reaching the full £12,000 takes 55 months of maximum contributions (£1,200 + 54 × £200), roughly four and a half years. Worked example: save the £1,200 opener plus £200 monthly for 30 further months and you hold £7,200; the bonus adds £1,800 (25%), giving £9,000 toward completion. The bonus is claimed by your conveyancer at completion and cannot be used for the exchange deposit — budget your own funds for exchange day. The scheme closed to new savers on 30 November 2019, but existing account holders can keep paying in until 30 November 2029 and must claim the bonus by 1 December 2030. Property price caps are £250,000 outside London and £450,000 within it, and the bonus applies only to first-time buyers purchasing with a mortgage. Interest earned inside the account also counts toward the bonus-eligible balance, and because the account is a cash ISA its rate resets with the market — as of mid-2026, remaining HTB ISA rates cluster roughly in the 3-4.5% range depending on provider.

HTB ISA vs LISA — Switch or Stay

For most buyers still years from purchase, the Lifetime ISA wins on raw bonus speed. A LISA accepts £4,000 per tax year and pays its 25% bonus monthly on contributions — up to £1,000 per tax year — while the HTB ISA's £200 monthly cap limits you to £2,400 a year (£600 of eventual bonus). Over three years: LISA contributions of £12,000 earn £3,000 in bonuses for £15,000 total; the HTB route yields £8,200 saved (£1,200 first month + 35 × £200) plus a £2,050 bonus — £10,250. The LISA bonus also lands in the account within weeks, where it can compound, rather than arriving at completion. But three catches argue for staying. First, the LISA's 25% withdrawal charge on non-qualifying withdrawals claws back more than the bonus: withdraw £1,000 for anything other than a first home or age 60+, and you receive £750 — an effective 6.25% loss of your own money. The HTB ISA has no penalty; you simply forgo the bonus. Second, timing: a LISA must be open 12 months before a penalty-free home purchase, so anyone buying within a year should not switch. Third, caps: the LISA covers properties up to £450,000 anywhere, versus the HTB ISA's £250,000 outside London — Londoners get £450,000 under both. You can transfer an HTB ISA balance into a LISA, but it counts toward the £4,000 annual LISA limit, so a large balance may take more than one tax year to move.