Inheritance Tax Late Penalties Rise 35% as Families Struggle With 122-Question Form

Inheritance tax late penalties issued by HMRC rose 35% over the past five years, climbing from 3,850 to 5,200 in 2024/25, according to Freedom of Information data obtained by TWM Solicitors. The total bill to bereaved families reached £3.1 million in that year, an average of £596 per case.

The increase reflects two pressures running in parallel: more families attempting to handle IHT returns without professional guidance, and a threshold freeze stretching back to 2009 that has drawn a growing number of modest estates into the tax net.

The IHT400: 122 Questions and a Tight Deadline

The main form for most taxable estates is the IHT400, which runs to 122 questions and frequently demands detailed financial and historical records. Under official GOV.UK guidance, it must be filed within 12 months of the date of death and, where probate is required, before a grant of probate can be obtained.

The penalty structure is unforgiving. An initial fine of £100 applies for missing the deadline, rising to a cumulative total of up to £3,000 after 12 months.

The IHT400 is rarely sufficient on its own. Depending on the nature of the estate, executors may need to complete more than 30 additional schedules covering assets ranging from business holdings to overseas property. Residential property requires a formal professional valuation; shareholdings must be valued using specific HMRC-prescribed methods. Market estimates do not meet the standard.

Tracing the full financial picture of a deceased person adds further delay. Identifying all bank accounts, investment holdings and historical gifts, some going back more than seven years under the seven-year gifting rule, can be slow work, particularly where banks only correspond by post.

Why Inheritance Tax Late Penalties Are Set to Rise Further

The nil-rate band has stood at £325,000 since 2009 and is confirmed to remain frozen until at least 2031. Standard Life modelling shows that, had the band risen with inflation since the freeze, it would stand at around £527,666 in 2026/27, roughly £200,000 above its current level. By 2030/31, the inflation-adjusted equivalent reaches around £593,893. The gap between those figures and the statutory £325,000 represents the threshold drag that has brought average properties in much of the UK into IHT territory without any other assets in play.

Families handling their own returns face a compounding risk: missing reliefs they are legally entitled to claim. Duncan Mitchell-Innes, partner and deputy head of private client at TWM Solicitors, said: ‘Reliefs aren’t applied automatically. People must actively claim reliefs and exemptions and find the evidence to support them where needed, which can be time-consuming. Without proper advice, families risk penalties and leaving valuable reliefs unclaimed.’

Gifts made from surplus income, or completed more than seven years before death, may qualify for exemption. Locating the supporting evidence is itself time-consuming, and some executors acting without advice are unaware these exemptions exist.

From April 2027, unused pension pots will be brought within the IHT net. Government estimates, as cited by Standard Life, put the number of additional estates pulled into IHT at 10,500, with around 38,500 facing higher bills than under previous rules. Standard Life’s own research, conducted among 2,000 UK adults in February 2026, found that 89% had little or no awareness of the change.

The Office for Budget Responsibility forecasts IHT receipts will reach £14.5 billion by the end of 2030/31, a rise of around 67% from 2025/26. An estimated £5.5 trillion is expected to pass between UK generations over the next 30 years. More of that wealth will travel through an IHT return, and the scope for inheritance tax late penalties will expand as personal representatives take on the added burden of coordinating pension paperwork alongside the rest of the estate.

The inheritance tax late penalties regime has not changed. The pool of people exposed to it keeps growing. Executors facing a 12-month deadline for the first time, with a 122-question form and pension trustees to chase, would do well to start well before the clock runs out.