Mortgages & Money2 min check

ISA Calculator (2026/27)

Estimate your ISA pot's growth using your monthly contribution, expected return and time horizon. Includes Lifetime ISA 25% government bonus.

Short answer

You can put up to £20,000 a year across all ISA types tax-free. A Lifetime ISA gives a 25% bonus on up to £4,000/year if used for a first home or kept until age 60.

Step 1 of 10%

Calculation method, coverage and version

Inputs used: ISA type, Existing balance, Monthly contribution, Annual return, Years to invest.
Calculation approach: The calculator applies the rules and assumptions described in “How it works” to the values you enter. Rounding can cause small differences from an official or provider calculation.
Coverage: Mortgages & Money. UK nations, tax treatment, local rules and provider criteria can differ; check the official sources shown below before acting.
Content version: No page-specific review date is currently published. Treat the result as indicative and verify current rules independently.

Not included unless explicitly requested: personal circumstances not entered, provider discretion, future rule changes, professional fees and case-specific exceptions. Read the full calculator methodology.

Primary sources and official verification

Use these official sources to verify current rules before acting. Coverage and dates can differ across England, Scotland, Wales and Northern Ireland.

See the sitewide source policy.

How it works

An ISA is a tax-free savings/investment wrapper. You can pay in up to £20,000 each tax year (split across Cash, Stocks & Shares, Innovative Finance, and Lifetime ISA). All interest, dividends and capital gains are tax-free, with no need to declare them.

Worked example

£300/month into a Stocks & Shares ISA at 5% for 25 years:

Contributed: £90,000
Final pot: ~£175,000
Growth: ~£85,000 — entirely tax-free

Who should use this

•Anyone with savings or investments outside an ISA
•First-time buyers (LISA gives 25% bonus)
•Higher-rate taxpayers minimising dividend/CGT exposure
•Long-term savers planning for retirement alongside a pension

Common mistakes

×Holding cash in a Stocks & Shares ISA long term (low returns)
×Forgetting the £20k allowance is per tax year, not per ISA
×Withdrawing from a non-flexible ISA and losing the allowance
×Using a LISA without realising the 25% withdrawal penalty

Frequently asked questions

What is the ISA allowance for 2026/27?▾

£20,000 across all adult ISAs combined. £9,000 for Junior ISA. LISA contributions count toward the £20,000.

Can I have multiple ISAs?▾

Yes — since April 2024 you can pay into multiple ISAs of the same type in one year, as long as total stays within £20k.

What's a Flexible ISA?▾

Withdrawals can be replaced in the same tax year without using more allowance. Not all providers offer this.

Cash ISA vs savings account?▾

Cash ISA is tax-free; standard savings get £1,000 (basic) or £500 (higher rate) Personal Savings Allowance, then taxed at marginal rate. ISAs win for higher-rate taxpayers or large balances.

What is a LISA?▾

Lifetime ISA — open between ages 18–39, contribute up to £4,000/yr, get 25% government bonus. Withdraw for first home (≤£450k) or after 60. Otherwise 25% penalty.

Does inheriting an ISA preserve tax-free status?▾

Spouses get an Additional Permitted Subscription equal to the deceased's ISA value, on top of their own £20k allowance.

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