ISAs shield dividends and gains from UK tax within the annual subscription limit (check HMRC for current limits).
Types of ISAs
Cash ISA for emergency funds, Stocks & Shares ISA for long-term investing, Lifetime ISA for first home or retirement (with rules and penalties for early withdrawal).
Using the Allowance
You can split the £20,000 across types in one tax year—plan around liquidity and time horizon.
Conclusion
Fund ISAs early in the tax year when possible to maximize time in market. Confirm limits and LISA rules on GOV.UK.