This ISA allowance calculator helps you estimate how much of the current tax year’s ISA limit may still be available and how a planned monthly contribution could fit across the months left. It is designed for UK ISA allowance planning rather than product comparison or investment advice. The result is only a guide because ISA rules, eligibility, provider processes and contribution timing can vary. Always check the latest GOV.UK limits and your provider’s records before relying on any figure shown here.
What this calculator assumes
- The annual ISA allowance entered is the relevant limit for the current tax year.
- The amount already used includes all current-year ISA contributions that count towards the allowance.
- Monthly pacing is a simple division of the remaining allowance by the months left.
- GOV.UK guidance and provider records should be checked before relying on the result.
How to read the allowance estimate
The allowance remaining is the annual ISA allowance entered minus the amount you say has already been used this tax year. The monthly amount to use the allowance spreads that remaining figure across the months left in the tax year. This can make the number easier to plan around, especially if you are comparing a regular contribution with a one-off payment. It is still only a planning estimate because the calculator does not know your full account history, payment dates, withdrawals, transfer status or provider-specific rules.
Why all ISA contributions matter
The ISA allowance is not a separate allowance for every provider or every account. For the 2026 to 2027 tax year, GOV.UK lists the adult ISA allowance as £20,000 and says it can be saved in one account or split across multiple accounts. That means the “allowance already used” field should include current-year contributions across all relevant ISAs, not just the platform in front of you. If you are unsure, your provider records and GOV.UK guidance matter more than this calculator.
What this calculator cannot check
This tool cannot confirm eligibility, validate provider records, model flexible ISA withdrawals or tell you whether a Stocks and Shares ISA is right for you. It also cannot know if pending deposits, transfers or withdrawals have changed the figure shown by your provider. Treat the output as a tidy way to sense-check the pace of contributions, then verify the real position before acting. Tax rules can change and this site is educational only, not financial advice.
Useful official sources
FAQs
What does the remaining ISA allowance show?
It shows an estimated amount that may still be available within the annual ISA allowance after subtracting the amount entered as already used.
Does this calculator know the current ISA limit?
It uses the allowance entered in the form. The default is set for the current adult ISA allowance at the time this page was prepared, but GOV.UK should be checked for the latest official figure.
Can this confirm how much I am allowed to pay in?
No. It is a planning aid only. The final position depends on the latest ISA rules, your eligibility, your full contribution history and provider records.
Should I try to use the full ISA allowance?
Not necessarily. The allowance is a limit, not a target. Whether to contribute, how much to contribute and which account to use depends on your own circumstances.