ISA growth calculator, 2026/27
Directors who have used up efficient salary and dividend planning often turn to ISAs for further tax-free saving. Enter a starting balance, monthly contribution and years invested to project your ISA balance, checked against the current annual ISA allowance.
The isa growth calculator runs on the rates and thresholds HMRC has published for the 2026/27 tax year, so the figures you see reflect the position your company is actually filing on rather than a historic set of bands. Change any input and the result recalculates immediately, with no sign-up and nothing sent anywhere.
If you are a director of a UK limited company, use it as a first look before a decision rather than as the decision itself. The annual ISA allowance for 2026/27 is £20,000, which can be split across ISA types but not exceeded in total. Real company positions bring in other income, reliefs, group structures and prior year adjustments that a single page of inputs cannot see, which is why the workings are written out below under personal finance & planning. Read those, then check the numbers against your own accounts, and speak to us if anything looks materially different from what you expected.
Last reviewed 12 September 2026 for the 2026/27 tax year. Reviewed by Waqas Sagar, Member of ICAEW, Fellow of ACCA, Fellow of AAT.
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Result, 2026/27
Projected ISA balance
Total contributed over the term
Annual ISA allowance headroom remaining
Based on the £20,000 annual ISA allowance.Estimated tax-free growth over the term
Illustration only, figures are based on the rates you have selected and the information entered. Please check your own position with us before acting.
Estimates for the 2026/27 tax year using published GOV.UK rates. Switch between 2026/27 and 2025/26 above.
How this is calculated
The projection compounds your starting balance and monthly contribution at the annual growth rate you choose, applied monthly, over the number of years entered. It then checks your annual contribution against the current ISA allowance of £20,000, flagging any headroom remaining if you are contributing less than the maximum.
Because ISAs are entirely free of income tax and capital gains tax on growth, dividends and interest, there is no tax deduction to apply within the projection itself, unlike a pension where relief and eventual tax on withdrawal both need to be modelled.
This is a simplified compounding model. Real stocks and shares ISA returns depend on the specific investments held and will vary year to year rather than following a smooth flat line.
ISAs alongside company and pension planning
For a director who has already made efficient use of the personal allowance, dividend allowance and pension annual allowance, an ISA is often the next efficient home for further savings, since it removes the need to think about tax on withdrawal at all, unlike a pension.
Unlike a pension, ISA funds can generally be accessed at any time without a tax charge, which makes an ISA more flexible for medium-term goals, though pensions retain the advantage of tax relief on the way in, which an ISA does not offer.
Making the most of the allowance
The ISA allowance does not carry forward; unused allowance from a previous tax year is simply lost once the tax year ends on 5 April, so contributing steadily through the year, rather than trying to catch up all at once, is usually more practical.
Married couples and civil partners each have their own full ISA allowance, so a household can effectively shelter twice the individual limit in ISAs each year between them.
What this means for your company
Treat the result as a planning figure for the 2026/27 tax year. If it changes what you were about to do, take a director's salary, a dividend, a large asset purchase or a filing decision, check it against your own accounts first. We can review the position with you and confirm the tax treatment before you commit.
Frequently asked questions
What is the ISA allowance for 2026/27?
The annual ISA allowance for 2026/27 is £20,000, which can be split between cash ISAs, stocks and shares ISAs, innovative finance ISAs and lifetime ISAs, subject to their own individual limits.
Does ISA growth need to be declared on my tax return?
No, income and gains within an ISA are entirely free of income tax and capital gains tax and do not need to be reported on a self-assessment return.
Can I contribute to an ISA as well as a pension?
Yes, they are separate allowances. Many directors use both: pension contributions for the up-front tax relief, and an ISA for tax-free growth with more flexible access before retirement age.
What happens if I do not use my full ISA allowance this year?
It is lost. The ISA allowance resets each tax year on 6 April and unused allowance cannot be carried forward to the following year, unlike the pension annual allowance which allows some carry forward.
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