Project the tax-free growth of your Stocks & Shares or Cash ISA with regular annual contributions.
All growth inside an ISA is free of UK income and capital gains tax, so this is a straightforward compounding projection: each year's contribution is added, then the whole balance grows at your expected return.
Illustrative estimate only, using simplified/rounded 2026/27 UK figures — not tax advice. Always confirm with HMRC or a qualified UK tax adviser.
An ISA (Individual Savings Account) shelters savings and investment growth from both Income Tax and Capital Gains Tax entirely, for life, with no need to declare anything on a tax return. The annual allowance for 2026/27 remains £20,000, which can be split across cash ISAs, stocks and shares ISAs, or a mix, but the combined total across all ISA types cannot exceed the £20,000 cap in a single tax year. Unused allowance does not carry forward — it resets to zero every 6 April.
Because growth compounds tax-free rather than being eroded by dividend tax or capital gains tax each year, the gap between an ISA and an equivalent taxable account widens the longer money stays invested. Withdrawals are also entirely tax-free at any time, unlike a pension, which makes an ISA the more flexible of the UK's two main tax-advantaged wrappers, at the cost of not receiving the upfront tax relief a pension contribution gets.
ISA providers are required to reject or flag over-contributions, and HMRC can void the tax-free status of the excess if it slips through, so it is worth tracking contributions carefully if you hold ISAs with more than one provider in the same tax year.
Only if your ISA is explicitly designated "flexible" by the provider — flexible ISAs let you replace withdrawn money in the same tax year without it counting against the £20,000 allowance again. Not all ISA providers offer flexible ISAs, so check before assuming.
Yes, contributions to a Lifetime ISA count within the overall £20,000 annual ISA allowance, though the Lifetime ISA itself has its own separate £4,000 sub-limit and comes with a 25% government bonus on contributions, plus withdrawal restrictions before age 60 except for a first home purchase.
ISAs are not automatically exempt from Inheritance Tax on death, though a surviving spouse or civil partner can inherit an additional ISA allowance equal to the deceased's ISA value, preserving the tax-free wrapper for that amount.