Cash ISA Allowance Planner for Under-65s: Last Full Year Before the £12k Cap (UK)

This article is general information about ISA allowances and planning, not personalised tax or financial advice. Rules can change. Check live pages on GOV.UK or speak to a qualified adviser before you act.

Who this is for

This is for UK savers under 65 who use (or are considering) a cash ISA and want a simple Google Sheets plan for 2026/27 — the last full tax year before the new cash subscription cap.

If your main goal is a first-home deposit with a Lifetime ISA, use our separate guide instead: House Deposit and LISA Tracker.

A cash ISA subscription here means money you pay into a cash ISA in a tax year (6 April to 5 April), counting towards your annual ISA limits.

What’s changing (plain English)

As of the live GOV.UK guidance and Tax Information and Impact Note published 17 September 2026:

You can still split the overall allowance across eligible ISA types (cash, stocks and shares, innovative finance, Lifetime ISA subject to its own rules). From 2027/28, if you are under 65, only £12,000 of that overall room can go into cash ISA subscriptions. Any remaining overall allowance can go to other eligible ISA types under the live rules — that is not a hard instruction to buy investments; it is how the limits interact on GOV.UK.

What else is changing (one screen): from April 2027 the government is also introducing anti-circumvention rules (for example a charge on interest on cash held in non-cash ISAs, and restrictions on transfers from non-cash ISAs into cash ISAs). Skim the factsheet if that might affect you — this page’s job is the allowance planner, not a deep dive on those rules.

Why 2026/27 matters

Until 5 April 2027, the current overall framework still applies for planning purposes: you can use your £20,000 annual ISA allowance in line with how ISAs work, including larger cash subscriptions than the under-65 cash cap that starts the next day.

So 2026/27 is the last full tax year before under-65s face the £12,000 annual cash ISA subscription limit.

ISA allowances are per tax year. Unused room does not roll into the next year — each 6 April resets the annual subscription limits (confirm on GOV.UK). If you want to use 2026/27 cash flexibility, the window closes at the end of that tax year.

Planner columns for a Google Sheet

Keep one row per contribution (or one monthly summary line):

1. Date
2. Tax year — e.g. 2026/27
3. Provider / account (optional)
4. Amount subscribed (£)
5. YTD cash subscribed (£) — running total for the tax year
6. Annual cash target (£) — your plan for the year
7. Remaining to target (£) — target minus YTD
8. Notes — standing order, lump sum, fixed vs easy-access (no product picks here)

At the top of the sheet, store:

• Overall ISA allowance for the year (check GOV.UK — £20,000 for 2026/27 at time of writing)
• Your planned cash vs other ISA split
• A reminder flag for 6 April 2027 if you will still be under 65

Monthly vs lump-sum rhythm (fictional example)

Example only — not a recommendation or a real person’s plan.

Another saver might put £5,000 in April and top up later. The sheet’s only job is: remaining = annual target − YTD, then decide whether the next payday transfer still fits your wider budget.

For the household money that funds those transfers, see How to Use a UK Monthly Budget Spreadsheet in Google Sheets or the seasonal UK Christmas Savings Tracker.

What this is not

• Not Lifetime ISA / first-home deposit maths — use the house deposit / LISA guide
• Not stocks-vs-cash investment advice
• Not a guide to sidestepping the 2027 rules

How a UkMoneySheets-style sheet fits

There is no Cash ISA calculator in the shop. The nearest sheet is the UK Net Worth tracker on UkMoneySheets, which can sit beside an ISA plan. It is not a Cash ISA calculator.

Files are Google Sheets (not Excel), usually delivered via a PDF with a Sheets link — then File → Make a copy.

A template organises numbers. Your provider and GOV.UK decide what actually counts as a subscription.

FAQ

When does the £12k cash ISA limit for under-65s start?

6 April 2027, per the Cash ISA limit reduction note. Re-check GOV.UK.

Is the overall ISA allowance still £20,000 after April 2027?

Yes — the TIIN keeps the overall annual ISA subscription limit at £20,000, with the cash portion capped at £12,000 for under-65s. Confirm on GOV.UK nearer the time.

Do people aged 65 or over keep a £20,000 cash ISA limit?

Yes, according to GOV.UK’s published note and factsheet. Entitlement to the higher cash limit applies from the start of the tax year in which you turn 65.

Does unused cash ISA allowance roll over to next year?

No — annual ISA subscription limits are per tax year. Unused room does not carry forward. See how ISAs work.

How is this different from a Lifetime ISA / house deposit plan?

A LISA has its own annual limit and first-home / later-life rules. This page is about cash ISA subscription caps for under-65s. For deposit planning, use the LISA / house deposit guide.

Is this tax or financial advice?

No. Education and organisation only.

Soft next step

1. Confirm your age band and the live limits on GOV.UK ISAs
2. Set a 2026/27 cash target and log subscriptions in a Google Sheet
3. From April 2027, re-check the under-65 cash cap before you set standing orders
4. If you want a sheet for the wider picture, the nearest fit is the UK Net Worth tracker on UkMoneySheets. It is not a Cash ISA calculator.

Plan the year. Verify the rules. Do not invent loopholes.