ISA Calculator

Calculate your tax-free savings with Cash or Stocks & Shares ISAs

Last updated: May 2026 · 2026/27 allowances

ISA Type

Contributions

£
£

Annual: £2,400

Interest Rate

%

Typical: 3-5% (2026/27)

ISA Value After 10 Years

£38,075

100% tax-free

Tax-Free Growth

£9,075

You Contribute
£29,000
Growth
£9,075
Tax saved: £3,630
Total Return
31.3%

Within Allowance

Annual contributions: £7,400 of £20,000 (2026/27)

ISA Allowance 2026/27

£7,400 of £20,00037%

Remaining: £12,600

Tax Saved vs Taxable Account

Basic Rate (20%)

£1,815

Higher Rate (40%)

£3,630

Additional (45%)

£4,084

* Tax on interest if held outside ISA

Growth Over Time

Year 1
£7,680
Year 2
£10,483
Year 3
£13,414
Year 4
£16,481
Year 5
£19,688
Year 6
£23,043
Year 7
£26,551
Year 8
£30,221
Year 9
£34,060
Year 10
£38,075
Contributions
Growth

Understanding ISAs

💷 Cash ISA

  • • Savings account with tax-free interest
  • • Capital guaranteed (FSCS protected)
  • • Fixed or variable rates available
  • • Easy access or notice accounts
  • • Best for: Short-term goals, emergency funds

📈 Stocks & Shares ISA

  • • Invest in stocks, bonds, funds
  • • Tax-free dividends & capital gains
  • • Higher potential returns (and risks)
  • • Not capital guaranteed
  • • Best for: Long-term growth (5+ years)

🏠 Other ISA Types

Lifetime ISA (LISA): 25% government bonus for first home or retirement (age 18-39)
Innovative Finance ISA: Peer-to-peer lending with tax-free returns

Annual Allowance 2026/27

£20,000

Total across all ISA types (except Junior ISAs)

⚠️ Coming April 2027

From 6 April 2027, the cash ISA limit will be cut to £12,000 for savers under 65 (Autumn Budget 2025). Your total £20,000 ISA allowance stays the same, only the cash portion is capped. Savers 65 and over keep the full £20,000 cash ISA limit.

✅ You Can

  • • Split between Cash & S&S ISAs
  • • Transfer old ISAs without losing tax-free status
  • • Withdraw and re-deposit (flexible ISAs)
  • • Have multiple ISAs (but only pay into one of each type per year)

❌ You Cannot

  • • Exceed £20,000/year total
  • • Open 2 Cash ISAs in same tax year
  • • Transfer cash into previous years' ISAs
  • • Use someone else's allowance

ISA allowance: £20,000 for 2026/27 tax year (6 April - 5 April)

Related calculators

Other free UK tools that follow on from this calculation.

Cash ISA vs Stocks & Shares ISA

Side-by-side projection of a Cash ISA vs Stocks & Shares ISA in real terms, with fees and the April 2027 cap.

Lifetime ISA Calculator

Project savings with the 25% government bonus for a first home or retirement.

Junior ISA Calculator

Project a child’s £9,000/year JISA pot at age 18, tax-free, Cash or S&S.

Future Value Calculator

Project how a lump sum or regular contributions grow over time with compound interest.