Less guesswork. More clarity.

Start with the things that matter to you

Enter the amount you want to place in a Cash ISA, choose instant access, a notice account or a fixed term, and tell us if you’re transferring an existing ISA.

New contributions assume you have enough unused ISA allowance. The total ISA allowance for 2026/27 is £20,000. Existing ISA money moved using a provider’s transfer process is treated separately from new contributions. We do not check your age, residency, other ISA subscriptions or provider application requirements.

Check the current ISA rules on GOV.UK

Turn percentages into pounds

For a rate that stays the same for a full year, estimated interest is your deposit multiplied by the annual equivalent rate.

AER already reflects annual compounding. We do not divide AER by 12 and compound it again. Where a bonus expires or a stated rate changes during the year, we calculate each period using its effective annual rate and duration, then combine the periods.

For effective annual rates, each period uses (1 + AER ÷ 100) raised to the fraction of the 12-month calendar horizon. For accounts explicitly marked as simple interest, period interest is added without compounding. The data must match the provider’s actual interest terms.

Estimates assume the full deposit stays in place, interest is retained or reinvested, and no further money is added. Variable rates are assumed unchanged except for stated rate changes and bonuses. Values are rounded to the nearest penny at the end.

The highest estimated return comes first

Accounts are excluded if they are inactive, outside your deposit limits, do not match your access type or fixed term, or do not accept a requested ISA transfer. Accounts restricted to existing customers are excluded because we cannot establish that eligibility from the form.

Eligible accounts are sorted by estimated interest over 12 months. Ties are ordered by provider name, then account ID. Affiliate links, commission and provider relationships play no role in this calculation.

A fixed account lasting more than 12 months remains a longer commitment. Its estimated first-year balance is not a maturity value you can withdraw without potential penalties. Notice periods, funding windows and early withdrawal rules appear in the account details.