The ISA Death Trap: Three Rules Executors Don't Know — and the Thousands Families Are Losing Because of It

A widow in Cheshire inherited her late husband's £85,000 stocks and shares ISA in 2023. The probate process took eleven months. By the time the estate was settled and the ISA assets were transferred, the account had been converted into a standard investment account and the tax-free status was gone. The growth on those assets — approximately £6,200 over the following two years — was subject to income tax and capital gains tax. Nobody told her there was a mechanism that could have prevented this. Her platform did not flag it. Her solicitor was not aware of it. She lost approximately £1,800 in unnecessary tax.

This scenario is not unusual. The rules governing ISA inheritance are among the least understood elements of UK personal finance — and the consequences of getting them wrong are permanent. Once the tax-free wrapper is lost, it cannot be reinstated.

Rule One: The Additional Permitted Subscription and the Clock That Starts at Death

When an ISA holder dies, their spouse or civil partner becomes entitled to an Additional Permitted Subscription (APS). This is a one-off allowance, equal to the value of the deceased's ISA at the date of death (or the value at the date the account is closed, if that is higher), that the surviving spouse can use to make an additional ISA contribution — over and above their own annual £20,000 ISA allowance.

The APS is not automatic. It must be claimed. And it is subject to a deadline.

Under current HMRC rules, the APS must be used within three years of the date of death, or within 180 days of the completion of the estate administration — whichever is later. In practice, for most estates, the three-year window is the binding constraint.

On an £85,000 ISA, the APS allows the surviving spouse to shelter a further £85,000 from tax — permanently. At a modest 5% annual return, that equates to £4,250 per year in tax-free growth indefinitely. Over a 20-year retirement, the compounded value of that tax shelter runs into the tens of thousands of pounds.

Miss the deadline, and the entitlement is gone. HMRC does not grant extensions for administrative delays, executor error, or platform failures.

Rule Two: The Continuing ISA and What Happens While Probate Drags On

Many executors and families assume that an ISA account is frozen at the point of death and stops generating returns. This is incorrect.

Under rules introduced in April 2018, a deceased person's ISA automatically becomes a Continuing Account of a Deceased Investor (commonly called a Continuing ISA). This account retains its tax-free status — meaning any interest, dividends, or capital growth within it remains exempt from income tax and capital gains tax — for up to three years from the date of death, or until the administration of the estate is complete, whichever comes first.

This is the mechanism that should have protected the Cheshire widow's assets. Had the platform correctly maintained the account as a Continuing ISA during the eleven-month probate period, the £6,200 growth would have remained within the tax-free wrapper.

The problem is that not all platforms implement this correctly, and fewer still communicate it clearly to executors. Research by the lang cat, a financial services consultancy, found that fewer than half of major UK investment platforms proactively inform executors of the Continuing ISA status when a death is registered. Several platforms default to closing the ISA and transferring assets to a cash account or general investment account within weeks of receiving the death certificate — a process that strips the tax-free status immediately.

Rule Three: The APS Cannot Be Inherited by Children — Only Spouses and Civil Partners

This distinction is widely misunderstood, including by solicitors who are not specialist financial planners.

The APS is available exclusively to the deceased's spouse or civil partner. Unmarried partners — regardless of the length of the relationship or cohabitation — do not qualify. Children and other beneficiaries do not qualify. The ISA assets they inherit are treated as ordinary cash or investments, fully subject to income tax and CGT on future growth.

For blended families, cohabiting couples, or estates where the primary beneficiary is an adult child rather than a surviving spouse, this rule has significant implications that should be addressed in financial planning well before death — not discovered during probate.

Which Platforms Are Failing Executors

For this article, Money Security reviewed the publicly available bereavement processes of eight major UK investment platforms. The findings are instructive:

Assessment based on publicly available platform documentation as of Q1 2026. Processes may differ in practice from published materials.

The variation is stark. Hargreaves Lansdown and Interactive Investor provide the most comprehensive documentation. Vanguard's postal-only process introduces delays that could, in theory, consume weeks of the three-year Continuing ISA window without the executor's awareness.

The Step-by-Step Guide for Executors

If you are handling the estate of someone who held ISAs, the following sequence applies:

Step 1 — Register the death with every platform immediately. Do not wait for probate to be granted. Registering the death triggers the Continuing ISA status and starts the clock. Most platforms require a certified copy of the death certificate and proof of your role as executor.

Step 2 — Confirm in writing that the account should be maintained as a Continuing ISA. Do not assume the platform will do this automatically. Send a written instruction (email or letter) explicitly requesting that the account retains its tax-free status pending completion of the estate.

Step 3 — Identify whether the deceased had a spouse or civil partner. If so, calculate the APS entitlement — it equals the higher of the ISA value at date of death or the value at account closure. Notify the surviving spouse of this entitlement and the three-year deadline.

Step 4 — The surviving spouse must open or identify an ISA with a platform that accepts APS transfers. Not all platforms accept APS contributions — confirm this before initiating the process. Hargreaves Lansdown, AJ Bell, Fidelity, and Interactive Investor all accept APS transfers. Check with Vanguard and smaller platforms individually.

Step 5 — Complete the APS subscription before the deadline. The APS form (available from the receiving platform) requires the deceased's date of death, the ISA provider's details, and confirmation of the entitlement amount. HMRC does not send reminders.

Step 6 — For non-spouse beneficiaries, seek specialist advice. A financial planner specialising in estate planning can identify whether there are legitimate structures — such as a deed of variation — that could redirect assets in a tax-efficient manner. This must be done within two years of the date of death.

The ISA Tax Year Deadline Is Also Relevant

With the 2025–2026 tax year closing on 5 April 2026, surviving spouses who are approaching the end of their three-year APS window — or who have recently received a bereavement notification from a platform — should treat the tax year end as an additional prompt. APS contributions can be made in the same tax year as a regular ISA contribution without double-counting, but the ISA subscription form must correctly identify the payment as an APS rather than a standard subscription.

What to Watch in the Coming Months

The Law Commission's review of the law of wills and succession, which has been ongoing since 2017, is expected to produce final recommendations in 2026. One area under consideration is whether cohabiting partners should gain greater rights in intestacy situations — which could, if enacted, affect APS eligibility. Any change would require primary legislation and is unlikely before 2027 at the earliest, but the direction of travel is worth monitoring.

The FCA's Consumer Duty obligations, which require platforms to demonstrate fair outcomes for consumers in vulnerable circumstances — a category that explicitly includes bereavement — may also prompt voluntary improvements in platform bereavement communications during 2026.

Closing verdict: The rules that protect ISA wealth through and beyond death are precise, time-limited, and almost entirely invisible to the families they are designed to help — and the only defence is knowing they exist before you need them.

This article is for informational purposes only and does not constitute financial advice. Your capital is at risk. Past performance is not a reliable indicator of future results.