Help to Buy ISA Calculator
Estimate your final house deposit and 25% government bonus. Remember, the scheme is closed to new accounts, but existing accounts can still save and claim.
Last updated: May 2026
Max £200/month by law.
Must claim bonus before Dec 2030.
Government Bonus (25%)
Total Home Deposit
£9,750
Important Deadlines
- • You can continue to save up to £200 a month into your account until November 2029.
- • You must claim your 25% government bonus by 1 December 2030.
- • The bonus is applied for by your solicitor at completion, meaning it cannot be used for the initial exchange deposit, only for the overall mortgage completion.
Reviewed by Sneha Iyer, CFP
•Certified Financial PlannerSpecializing in wealth management and retirement planning. Sneha validates the investment projection models and compound interest algorithms used across our financial tools. All mathematical models and regulatory data points have been verified for the current 2026 fiscal period.
How the Help to Buy ISA Works
The Help to Buy ISA was a government scheme launched to help first-time buyers get on the property ladder. Although it closed to new applicants in November 2019, if you already have an account, you can keep saving into it until November 2029.
The government tops up your savings by 25% (up to a maximum bonus of £3,000). To get the maximum bonus, you need to save £12,000. You must have at least £1,600 saved to trigger the minimum £400 bonus.
How to use this calculator
- 1Current Balance — Check your banking app and enter how much you currently have saved in your HTB ISA.
- 2Monthly Savings — You are allowed to deposit a maximum of £200 per calendar month.
- 3Time Horizon — Estimate how many months until you plan to complete on a house purchase.
Formula & example
The 25% Bonus Rule
Example: You currently have £8,000 and save £200/mo for 20 months.
- Final Balance: £12,000
- Government Bonus: £3,000
- Total Deposit Added to Mortgage: £15,000
Benefits
Guaranteed 25% Return
The government bonus is guaranteed, plus you earn tax-free interest from your bank on top.
Penalty-Free Withdrawals
Unlike the Lifetime ISA, you can withdraw your money from a Help to Buy ISA at any time without a 25% penalty. You just won't get the bonus on the withdrawn amount.
Use cases
Planning a Purchase
Calculating exactly how much of a mortgage you will need based on your total deposit + bonus.
Should I switch to LISA?
Deciding if you should transfer your HTB ISA into a Lifetime ISA (LISA) which allows £4,000/year instead of £200/month.
Frequently asked questions
Can I use the bonus for the exchange deposit?+
No. This is a common misconception. The bonus is applied for by your solicitor between exchange and completion, meaning it is added to your overall mortgage completion funds, not the 10% cash deposit needed on the day you exchange contracts.
What is the maximum property price?+
You can only use the Help to Buy ISA bonus on properties up to £250,000 outside London, and up to £450,000 inside London.
Should I switch to a Lifetime ISA (LISA)?+
If you are buying a home worth more than £250k (outside London) but under £450k, the LISA is better. The LISA also allows you to save £4,000 a year instead of £2,400. However, the LISA has a strict 25% withdrawal penalty if you don't use it for a home/retirement, whereas the HTB ISA is flexible.