UK ISA Research

Long-form research notes drawing on HMRC ISA statistics, FCA data, and historical UK market series. Updated as new data publishes.

What can you learn from PlainISA research?

What this research covers

PlainISA research works the 2026/27 HMRC ISA allowance set (£20,000 overall · £4,000 LISA · £9,000 Junior across 5 wrapper types) into 3 published notes.

2026/27
HMRC tax year in rate set
£20,000
overall ISA allowance
£4,000
LISA annual allowance
3
published studies

Studies below answer one wrapper-arithmetic or returns question each from the live HMRC rate registry; they are descriptive notes, not personal investment advice.

Cash ISA vs Stocks & Shares ISA, Long-Run Returns

A multi-decade analysis of typical real returns: cash 1.5-2% real vs S&S 4.5-5% real, with volatility-adjusted comparisons.

The LISA Net-Loss Arithmetic

When the 25% Lifetime ISA bonus turns into a net loss after early-withdrawal penalty, the 6.25% breakeven floor.

UK ISA Wrapper Mix Shift 2014-2024

How the ISA wrapper distribution shifted from 80% Cash to 60% Cash + 35% S&S + 5% other over a decade.

Download the HMRC ISA wrapper statistics extract cited on this page: hmrc-isa-wrapper-statistics.csv (Open Government Licence v3.0).

The figures in this guide are rendered from our ISA rules database (gov.uk and the HMRC ISA Managers Guidance Notes); the explanation around them is written prose rather than database output. Read our editorial standards and corrections policy, the methodology behind these numbers, or report a data error.

Primary statutory sources: gov.uk’s Individual Savings Accounts guidance and HMRC’s ISA Managers Guidance Notes. Historical context is checked against HMRC’s annual ISA statistics.

PlainISA publishes ISA reference data and projection tools for information only. It is not financial advice and not a personal recommendation, projections are illustrations rather than forecasts, and tax rules and allowances change, so check the current position on gov.uk or with an FCA-authorised adviser before you act. Appropriate use.