ISA Calculator UK for the 2026/27 tax year
This ISA calculator is built for the 2026/27 UK tax year. It helps you work out how much ISA allowance you have left, whether your planned contributions fit within the annual limit, and what your projected balance could look like by the end of the tax year.
You can use it for a standard adult ISA, a Lifetime ISA (LISA), a Junior ISA (JISA) or a Child Trust Fund (CTF). For Lifetime ISAs, the tool also estimates the government bonus based on the contributions you enter.
2026/27 ISA allowances used in this calculator
For the 2026/27 tax year, the main adult ISA subscription limit is £20,000. The Junior ISA and Child Trust Fund subscription limits are £9,000. The Lifetime ISA limit is £4,000 and counts within the overall adult ISA limit, with a 25% government bonus on eligible LISA contributions up to a maximum £1,000 bonus for the year.
What this ISA calculator shows
- Relevant annual allowance for the account type selected
- How much allowance you have already used this tax year
- Your remaining allowance
- Whether your planned lump sum and monthly contributions fit within the limit
- Your maximum extra monthly contribution based on the months remaining
- Estimated Lifetime ISA bonus where relevant
- Projected end-of-tax-year balance and a monthly chart
Useful ISA rules to keep in mind
The calculator focuses on annual subscription limits, but some ISA rules depend on the product type. For example, Lifetime ISAs have age rules and a separate annual LISA cap within the overall adult ISA allowance. Junior ISAs and Child Trust Funds are for children, while adult ISAs are for adults. Flexible ISA withdrawals may also affect how much of your allowance you can still replace during the same tax year if the account is flexible.
This tool is for illustration only and is designed to help with planning. Actual provider rules, bonus timing, transfer processes and account eligibility can vary, so always check product terms before acting.