Most families only think about inheritance tax when it’s already too late to do much about it. A parent passes away, a house gets valued, and suddenly the estate is sitting above a threshold nobody expected to breach. The tax bill lands, and so does the regret.
What makes this especially hard is that many of the costliest mistakes are not dramatic failures. They’re quiet oversights. A gift made the wrong way. A pension left unreviewed. A threshold frozen in place while property values kept rising. The money walks out the door before anyone fully understands why.
The Frozen Threshold Trap Nobody Talks About
The standard inheritance tax threshold in the UK is £325,000 per person, and above that amount, an estate is usually taxed at 40%. That number sounds like it belongs to wealthy households. The problem is the threshold hasn’t moved in a very long time.
This threshold has been frozen at £325,000 since April 2009 and is set to stay frozen until 5 April 2031. Property values have roughly doubled since 2009 while the threshold has stayed the same, meaning more estates are pulled into the tax each year without anything changing about the rules themselves.
Inheritance tax is not just a concern for the very wealthy. Rising property values and frozen thresholds mean that more families are affected each year. A modest semi-detached home, some savings, and a small pension pot can push an ordinary estate well past the limit without anyone expecting it.
The Gifting Mistake That Can Come Back Years Later
People can give away lump sums of any size through what are known as potentially exempt transfers. If they survive for seven years after making the gift, it will normally fall outside their estate for inheritance tax purposes.
If they die within those seven years, the gift can be brought back into the inheritance tax calculation, potentially leaving families with an unexpected bill. Many families assume that giving money away is automatically safe. It isn’t, and the consequences of getting it wrong can fall on the person who received the gift, not just the estate.
The critical issue is that the bill does not necessarily fall on the estate. Instead, it lands on the person who received the gift. That means someone who accepted money years ago in good faith can find themselves facing a tax demand after a bereavement.
Giving Away Your Home While Still Living in It
Common mistakes include giving away your home but still living in it, or giving cash to a family member who then buys a property for you to use. This arrangement, known legally as a “gift with reservation of benefit,” is one of the most frequently misunderstood traps in estate planning.
HMRC figures show that between 2021 and 2026, close to 2,500 gifts worth a total of £840 million were considered to have had “reservation of benefit.” These gifts, with an average value of around £338,840, were therefore not exempt from death duties, landing families with an estimated total tax bill of £336 million.
The logic seems sound on the surface: give the house to the children while you’re still alive and the value leaves the estate. But HMRC treats it as though the gift never happened if you continue to benefit from it. The house stays in the estate for tax purposes regardless.
The Cohabiting Couple Assumption
Even where the home is jointly owned, a cohabiting couple might not realise that, as they are unmarried, the share of the property left to the surviving partner will deplete or wipe out their nil-rate band on its own, leaving all other assets exposed to inheritance tax.
Marriage and civil partnership have certain tax benefits, but the spousal exemption from inheritance tax at death is probably the most powerful. Unmarried couples, no matter how long they have been together, do not benefit from this exemption automatically. The assumption that long-term partners are treated like spouses by tax law is simply wrong.
An estate won’t be taxed if you leave it to your spouse or civil partner, or an exempt charity. Without that formal legal status, even a lifelong partner is treated as a stranger in the eyes of inheritance tax law.
Forgetting to Update Beneficiary Designations
One common mistake is uncoordinated assets, like forgetting to update beneficiaries on retirement accounts or insurance policies. This happens quietly over the years as circumstances change: a divorce, a remarriage, children from a second relationship. The documents just don’t get updated.
Failing to update after divorce is particularly damaging. Ex-spouses may inherit unintentionally, while children from prior marriages may be excluded altogether. The will might be perfectly crafted while the pension and life insurance policy are still naming the wrong person entirely.
This kind of oversight can cost families enormously, both in misdirected assets and unnecessary tax exposure. It’s one of the most preventable mistakes and also one of the most common.
Pensions Are About to Become a Serious Problem
From April 2027, pensions will become taxable under inheritance tax for the first time. For years, many savers treated their pension pot as a clean, tax-efficient way to pass money to their family. That assumption needs urgent revisiting.
The government raked in £8.5 billion in inheritance tax receipts in 2025/26, with the Office for Budget Responsibility forecasting the tax take will increase to almost £15 billion by 2030/31. Rising equity and house prices, frozen tax thresholds, and the impact of unused pensions falling under the scope of inheritance tax from April 2027 will, in part, cause the rise.
The only way to keep pensions free of inheritance tax with any certainty will be to leave them to a spouse or civil partner. Anyone with a significant pension pot and children as intended beneficiaries needs to review their plans before April 2027.
The Business and Farm Relief Change Many Owners Missed
From 6 April 2026, individuals are only entitled to 100% agricultural property relief and business property relief on assets worth up to a maximum of £2.5 million. The UK Government announced this threshold increase from the original £1 million cap.
Any value in excess of £2.5 million will qualify for 50% relief, meaning there is an effective 20% inheritance tax rate on death. Under previous rules, these assets would have been fully relieved. For family farms or small businesses valued above the threshold, this is a major structural shift that many owners have not yet planned for.
As a result, a significant portion of the value of farms and businesses may become subject to an effective inheritance tax rate of up to 20%. Estates that assumed full relief now face partial liability, and that distinction can translate into very large sums of money.
The Rising Volume of HMRC Investigations
Nearly 5,000 bereaved families were investigated by HMRC in the 2025/26 tax year as part of a crackdown on underpaid inheritance tax. The number of formal inquiries hit a six-year high, with around 770 more investigations launched than in the previous 12 months.
Of the 4,940 families targeted for an inquiry, roughly four in ten had their inheritance tax bill adjusted. That rate suggests these aren’t speculative audits. HMRC is finding genuine underpayment at a significant scale.
The inheritance tax bill must be paid by the end of the sixth month after death, or the amount owed begins to accrue interest at a rate of 7.75% a year. A typical investigation lasts between six and 12 months, but complicated cases can drag on for several years. Families caught in an investigation often deal with financial stress at precisely the worst moment.
Holding Wealth in the Wrong Structures
One of the most common mistakes is failing to make full use of the nil-rate band allowance. Assets held in taxable estates can increase the overall inheritance tax liability, particularly when investments have grown significantly in value. Without regular reviews, portfolios may become inefficient for estate planning, leaving beneficiaries with a reduced inheritance.
AIM shares previously attracted 100% business property relief after a two-year holding period, making them a popular inheritance tax planning tool. From 2026, that 100% relief no longer applies. AIM shares are now subject to the same 50% relief cap that applies to other business assets above the £2.5 million threshold. For portfolios that relied on AIM shares as an inheritance tax shelter, this is a material change.
Reviewing how assets are held, not just what assets are held, is often where real savings can be found. Many families get this right in the early stages of planning and then never revisit it as laws evolve.
Leaving It Too Late to Plan at All
Perhaps the most costly mistake is leaving planning until too late. Inheritance tax law contains provisions that require time to work properly. The seven-year gifting rule is one. Using trust structures effectively is another. None of these can be activated after someone has died.
High-net-worth families often spend decades building substantial assets, only to lose a substantial portion of that wealth due to preventable tax exposure, legal disputes, and structural planning failures. In 2026, this risk is even higher. With major tax law uncertainty, outdated or poorly executed estate plans are silently eroding family legacies.
Against this backdrop, even simple planning errors can prove costly. Many families unknowingly reduce the wealth passed on to loved ones by overlooking key exemptions, misunderstanding gifting rules, or failing to plan early enough. Getting proper advice while there’s still time to act is not just useful. In many cases, it’s worth thousands of pounds.
The Takeaway
Inheritance tax rarely punishes the obviously reckless. More often, it catches the quietly unprepared. Thresholds that haven’t moved in over fifteen years, pension rules rewritten midstream, gifting mistakes made in good faith decades earlier: these are not exotic problems reserved for the very wealthy. They affect ordinary families with ordinary assets in increasing numbers.
The uptick in investigations comes as frozen tax thresholds have dragged more people into paying death duties, with the number of families caught in the net expected to nearly double by 2030/31. The trajectory is clear and it doesn’t rely on any dramatic policy change to continue.
The best time to review an estate plan is always before it becomes urgent. The second-best time is now, while there are still decisions to make, reliefs to use, and time on your side.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.