UK ISA Decision Engine 2026/27
Your ISA, Sorted in 60 Seconds
Executive Summary
In a nutshell
A scenario-based decision engine that walks under-65 UK savers through the once-in-a-generation ISA shake-up: the last £20k Cash ISA year (2026/27), the £12k cap landing April 2027, the Lifetime ISA being replaced by a first-time-buyer-only product (consultation early 2026, launch April 2028), and how to optimally split contributions across Cash ISA, Stocks & Shares ISA, LISA top-up, GIA and pension. Output is a personalised playbook with affiliate-linked provider recommendations (Trading 212, InvestEngine, Moneybox, Tembo, Plum, HL). The pain is acute, the deadline is hard-coded into legislation, and most existing tools are static articles or single-product calculators — there's a real gap for a multi-input, multi-output decision engine.
The Story
Meet the user
Naz is thirty-four, a marketing manager in Manchester, and he's been doing the "responsible thing" for years — sticking £400 a month into a Cash ISA at 4.3%, topping up his Lifetime ISA when he can, and occasionally buying premium bonds because his nan said they were a good idea. Then the 2025 Autumn Budget happened, and his WhatsApp groups exploded. From April 2027 the under-65 Cash ISA limit drops to £12k. The Lifetime ISA he's been quietly building is being scrapped — replaced by a first-time-buyer-only product in 2028 that won't help his retirement plans at all. He's read seven articles, three of them contradicting each other, and he still doesn't know what to actually *do*. Should he max his Cash ISA this year? Cash out his LISA before the rules change and pay the 6.25% penalty? Open a SIPP instead? He just wants someone to tell him: given his situation, his goals, his timeline — what should he do, in order, this week?
Then a colleague forwards him a link to ISADecide. He answers eight questions — age, income, savings, ISA balances, time horizon, first-home goal, retirement plan — and twelve seconds later he's looking at a personalised playbook: "Top up £6,400 to your Cash ISA before 5 April 2027 (last chance for the full £20k). Keep your LISA open — you're under 40, you'll get the 2027 migration window without penalty. Open a Stocks & Shares ISA at InvestEngine for the £8k you'd otherwise lose to the new cap. Don't bother with new Premium Bonds at your tax band." Each step has a "Why this?" expander and an affiliate-linked "Open this account" button. For the first time in months, the noise stops.
Scores
How does this idea stack up?
7.7/10
Top keywords ("lifetime isa uk" 12,100/mo, "best stocks and shares ISA UK" 8,100/mo trending up sharply, "cash ISA vs stocks and shares ISA" 1,900/mo) plus a £700B+ adult ISA market. £5.3bn paid into LISAs alone in 2023/24.
Real frustration in UK personal finance communities. Confusing, contradictory advice across providers. 74,000 LISA penalty hits in 2022/23 averaging £11,000 each. People actively asking "what should I do?"
Pure decision-tree logic on top of public ISA rules. No regulated data, no licensing required (general guidance, not advice). MVP ships in 2-3 weeks with Next.js + Supabase + Stripe (optional premium tier).
The Cash ISA cut takes effect April 2027 — there's a 12-month "use it or lose it" window. The LISA consultation opens early 2026 and the replacement lands April 2028. This is the regulatory tailwind moment.
The hot deadline window is 2026/27 → 2028, but ISA decision-making is evergreen — annual allowance refresh every April, plus rules will keep changing. Re-positionable as "ISA Decision Engine" full stop.
Standard web stack, decision tree + provider DB. No special infrastructure. Solo-buildable. Ongoing work is keeping rules current (annual).
Strongest
Timing and Feasibility
There's a hard regulatory deadline 12 months out and the build is trivial. The market window has opened *now* and won't repeat.
Watch out
Durability
Once 2027/28 lands, urgency drops. Roadmap must extend the tool to evergreen "annual ISA decision" + retirement planning to retain ARR.
Pain Point
The problem
“The increasing likelihood of paying an effective 6.25% penalty on your hard-earned savings if your dream home exceeds this threshold makes the account much less appealing. Around 74,000 savers were hit with penalties in 2022-23, with some penalties averaging an eye-watering £11,000 each.”
— MoneyWeek/MSE coverage of the LISA Treasury Committee report
The pain is multi-dimensional. First, the **information overload** — every Cash ISA provider, every IFA, every newspaper has a different angle on the 2026/27 changes. Search demand for "cash ISA vs stocks and shares ISA" is steady at ~1,900/mo with monthly peaks at 2,900 — people are explicitly trying to decide. Second, the **deadline pressure** — the 2026/27 tax year is the *last* year an under-65 saver can get £20k into a Cash ISA. From 6 April 2027 it's £12k, with the remaining £8k forced into Stocks & Shares ISA, LISA, or Innovative Finance ISA territory. Third, the **LISA paralysis** — 1.6 million people have a LISA, the product is being scrapped, and the consultation in early 2026 will determine whether existing holders get a penalty-free migration window. People genuinely don't know whether to keep contributing, pause, or withdraw and eat the 6.25% penalty.
The fourth and most under-served pain is **strategy synthesis**. A typical 30-something has multiple goals (house deposit, pension, emergency fund), multiple existing accounts (Cash ISA, LISA, maybe a workplace pension, Premium Bonds), and finite cash flow. Existing tools handle one product at a time — MoneySavingExpert lists best buys, Hargreaves Lansdown calculates a single ISA's growth, scrimpr.co.uk compares platform fees. None walk a user through "given everything you've got, what should you do this tax year?" That's the gap.
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