ISA Calculator UK for the 2026/27 tax year
This ISA calculator UK helps you check how much of your 2026/27 ISA allowance you have used, how much you still have available, and whether your planned contributions fit within the relevant annual limit. It is designed for savers who want a quick planning view across adult ISAs, Lifetime ISAs (LISAs), Junior ISAs (JISAs) and Child Trust Funds (CTFs).
If you are using a Lifetime ISA, the calculator can also estimate the government bonus on eligible contributions. That makes it useful both for general ISA allowance checks and for planning how much to contribute before the end of the tax year.
What this calculator includes
- Adult ISA, Lifetime ISA, Junior ISA and Child Trust Fund allowance checks
- Remaining annual allowance based on contributions already made
- Planned lump sum and monthly contribution modelling
- Estimated Lifetime ISA government bonus where relevant
- Projected end-of-tax-year balance using your growth assumptions
- Flexible ISA withdrawal input where applicable
How it works
The calculator starts with the annual allowance for the account type you select, then compares it with the subscriptions you have already made this tax year. It then adds any planned lump sum and monthly contributions to show whether you remain within the limit and how much allowance is left.
For Lifetime ISAs, it also estimates the bonus based on eligible contributions. If you enter a current balance and annual growth rate, the tool projects a possible value by the end of the tax year so you can compare different saving patterns.
Why your results may vary
This is a planning tool, so real outcomes may differ depending on provider rules, contribution timing, bonus payment timing, transfer rules, market performance, and whether a product is flexible. Some rules also depend on your age and product eligibility, especially for Lifetime ISAs and child accounts.
Who it’s for
- Savers checking how much ISA allowance they have left this year
- People planning Lifetime ISA contributions and bonus estimates
- Parents reviewing Junior ISA or Child Trust Fund limits
- Anyone comparing lump sum and monthly ISA contribution options
ISA examples
- £5,000 already contributed with £300 per month planned for 6 months
- Lifetime ISA saver contributing £4,000 and estimating the 25% bonus
- Junior ISA planning using the annual child allowance limit
- Adult ISA saver checking how much room is left before the tax year ends
Important note
This calculator provides estimates only and does not constitute financial, tax or legal advice. Always check official product terms and current provider rules before making decisions.
Use the calculator above to check your ISA allowance, test different contribution amounts, and estimate how your balance could change by the end of the tax year.