UK Probate and IHT400 Form 2026: Reporting an Estate to HMRC

What Is the IHT400 and When Is It Required?

The IHT400 -- officially titled the Inheritance Tax Account -- is the form used to report a deceased persons estate to HMRC when the estate does not qualify as an excepted estate. Completing an IHT400 is a legal obligation for personal representatives (executors or administrators) in these circumstances, and failing to file correctly can result in penalties and interest.

For 2026/27, an estate must generally be reported on IHT400 if:

• The total value of the estate (including gifts made in the seven years before death) exceeds the Nil Rate Band (NRB) of GBP 325,000
• The estate exceeds GBP 500,000 where the Residence Nil Rate Band (RNRB) of GBP 175,000 is available
• The deceased was domiciled in the UK and had overseas assets above GBP 100,000
• There are complex matters such as trusts, business or agricultural property relief claims, or significant gifts within seven years of death

If the estate qualifies as excepted -- broadly, if it is below the thresholds and is straightforward -- you may use the shorter IHT205 or simply confirm the estate is excepted when applying for probate. HMRC updated excepted estate rules from 1 January 2022 to reduce the number of low-value estates needing full reporting, so it is worth checking whether full IHT400 reporting is actually required for the estate you are administering.

The Nil Rate Band and Residence Nil Rate Band for 2026/27

The two main IHT allowances you need to understand before completing the IHT400 are:

Nil Rate Band (NRB): GBP 325,000

The NRB is the threshold below which no IHT is charged. It has been frozen at GBP 325,000 since 2009 and is currently frozen until at least 2030. Every individual has their own NRB. A surviving spouse or civil partner can inherit the deceased spouses unused NRB through a Transferable NRB claim on form IHT402.

Residence Nil Rate Band (RNRB): GBP 175,000

The RNRB applies when the deceased owned a qualifying residential property (their home or a former home) and left it, or an equivalent cash value, to direct descendants. The maximum RNRB is GBP 175,000 per person. Again, unused RNRB from a predeceased spouse can be transferred using form IHT436.

Combined, a couple can pass up to GBP 1 million (GBP 325,000 x2 NRB + GBP 175,000 x2 RNRB) free of IHT -- provided the conditions are met and neither spouse had previously used any of their allowance.

Taper on large estates

The RNRB tapers by GBP 2 for every GBP 1 by which the net estate exceeds GBP 2 million. An estate worth GBP 2.35 million receives no RNRB at all. This taper applies before any transferable RNRB is added.

The IHT rate on taxable estates above the available NRB and RNRB is 40%. A reduced rate of 36% applies if at least 10% of the net estate is left to qualifying charities, which can produce a significant saving on large estates.

The IHT400 Deadline and Interest on Late Payment

The IHT400 must be submitted, and any IHT due must be paid, within six months of the end of the month in which the death occurred. This is a hard statutory deadline.

Examples:

• Death on 4 January 2026 -- deadline 31 July 2026
• Death on 28 November 2025 -- deadline 31 May 2026
• Death on 1 June 2026 -- deadline 31 December 2026

HMRC charges interest on any IHT not paid by the deadline. For 2026/27, the interest rate on late paid IHT is the standard HMRC late payment rate, which is linked to the Bank of England base rate plus 2.5 percentage points. Interest accrues daily from the due date, so early payment reduces the total cost.

Personal representatives can make a payment on account of IHT before the full IHT400 is submitted if they need more time to gather valuations. This stops the interest clock running on the amount paid.

The 12 Supplementary Pages of IHT400

The IHT400 itself is only part of the picture. HMRC requires additional supplementary schedules (the Dxxx and IHTxxx series) depending on the assets in the estate. Key schedules include:

• IHT401 -- Domicile outside the UK
• IHT402 -- Claim to transfer unused NRB from a late spouse or civil partner
• IHT403 -- Gifts and other transfers of value within seven years of death
• IHT404 -- Jointly owned assets
• IHT405 -- Houses, land, buildings, and interests in land
• IHT406 -- Bank and building society accounts
• IHT407 -- Household and personal goods
• IHT408 -- Household and personal goods donated to charity
• IHT409 -- Pensions
• IHT410 -- Life assurance and annuities
• IHT411 -- Listed stocks and shares
• IHT412 -- Unlisted stocks and shares, and control holdings
• IHT413 -- Business or partnership interests and assets (for Business Property Relief)
• IHT414 -- Agricultural relief
• IHT415 -- Interest in another estate
• IHT416 -- Debts owed to the estate
• IHT417 -- Foreign assets
• IHT418 -- Assets held in trust
• IHT419 -- Debts owed by the deceased
• IHT421 -- Probate summary (submitted alongside the grant of probate application)
• IHT435 -- Claim for RNRB
• IHT436 -- Claim for transferred RNRB

Not every estate needs all of these, but a moderately complex estate -- for example, one with property, a pension, some listed shares, and one or two joint accounts -- will easily need six to eight supplementary schedules.

Valuing the Estate

Every asset in the estate must be valued at open market value on the date of death. This means the price a willing buyer would pay to a willing seller in the open market, not a distressed or forced sale price.

Property

Residential property should be valued by a qualified surveyor or estate agent. HMRC has the power to challenge property valuations and refer them to the District Valuer. If the property is later sold for more than the probate value, this can trigger an IHT or CGT adjustment depending on the timeline.

Shares and investments

Listed shares are valued using the closing price on the date of death (or the lower of closing and opening prices on a Stock Exchange business day). For ISAs and dealing accounts, the investment provider will usually supply a date-of-death valuation.

Personal property

Household contents and personal possessions should be valued realistically. HMRC may query valuations that appear to significantly understate the value of contents.

Debts

Debts owed by the deceased -- mortgages, credit card balances, loans, and reasonable funeral expenses -- are deducted from the gross estate to arrive at the chargeable estate.

Paying IHT Before Probate -- the Practical Problem

One of the most common practical difficulties in estate administration is that you need to pay IHT before you can get probate, but the estate assets are locked until probate is granted.

There are three main solutions:

Direct Payment Scheme

Many UK banks, building societies, and NS&I allow funds to be paid directly to HMRC from the deceased persons accounts before probate is issued. The personal representative writes to the institution, provides an IHT reference number obtained from HMRC, and the institution transfers the funds. This covers the IHT liability without the executor needing to use personal funds.

Personal representatives own funds

Executors can pay IHT from their own money and reclaim it from the estate once probate is issued. This is straightforward in principle but requires the executor to have sufficient liquid funds and a willingness to be temporarily out of pocket.

Instalment option for property

Where the estate includes UK property -- residential or commercial -- personal representatives can elect to pay the IHT attributable to that property in ten annual instalments rather than as a lump sum. The first instalment is due at the normal six-month deadline. Interest applies to each instalment. If the property is sold before all instalments are paid, the outstanding balance becomes due immediately.

Grant of Probate -- Timeline and Process

Once the IHT400 and any required tax payment have been submitted, HMRC will issue a form IHT421 (the probate summary) back to the executors. You then submit this, along with the original will and the probate application form (PA1P for probate where there is a will, PA1A where there is no will), to the Probate Registry.

Current grant of probate waiting times in England and Wales vary but have been running at several weeks to months depending on complexity and the volume of applications the Probate Registry is handling. For straightforward estates where the IHT has been paid and accepted by HMRC, grants are often issued more quickly. Complex or contested estates can take considerably longer.

In Scotland, the equivalent process is Confirmation rather than probate, administered through the Sheriff Court. The Inheritance Tax process and IHT400 requirements are the same, but the court process differs.

Business Property Relief and Agricultural Property Relief

Two important reliefs can reduce or eliminate IHT on certain types of asset:

Business Property Relief (BPR)

Qualifying business assets can attract either 100% or 50% BPR, effectively eliminating or halving the IHT charge. From April 2026, the government announced changes to BPR limiting 100% relief to the first GBP 1 million of qualifying assets per estate, with a 50% rate applying above that. This is a significant change for owners of large family businesses and AIM portfolio investors. Claim BPR on form IHT413.

Agricultural Property Relief (APR)

Agricultural land and buildings used for farming can qualify for either 100% or 50% APR depending on whether the owner or a tenant farms the land. Similar restrictions to BPR were announced alongside the BPR changes. Claim APR on form IHT414.

Both reliefs are complex and it is strongly advisable to seek specialist advice where they are involved.

Calculating the IHT Liability

Here is a straightforward example for 2026/27:

• Gross estate: GBP 850,000 (house GBP 500,000, investments GBP 250,000, savings GBP 100,000)
• Less debts (mortgage GBP 50,000, funeral GBP 8,000): GBP 58,000
• Net estate: GBP 792,000
• Less NRB: GBP 325,000
• Less RNRB (house left to children): GBP 175,000
• Taxable estate: GBP 292,000
• IHT at 40%: GBP 116,800

The same estate with a transferred NRB and RNRB from a predeceased spouse would have a combined exemption of GBP 1 million, resulting in nil IHT.

Use the CalcHub Inheritance Tax Calculator to model different estate structures, gifts, and relief scenarios before you begin completing the IHT400.

Common Mistakes to Avoid

Undervaluing assets

HMRC cross-checks property valuations against Land Registry data and will investigate where the probate value appears inconsistent with local market prices. An undervaluation can result in additional IHT, interest, and penalties.

Missing lifetime gifts

Gifts made within seven years of death are chargeable transfers that must be reported on IHT403. Many executors are unaware of all gifts the deceased made, particularly cash gifts. Ask family members and check bank statements for large outgoings.

Ignoring jointly owned assets

Assets held jointly -- bank accounts, property in joint names -- must still be declared on the IHT400 even though they pass automatically to the surviving owner by survivorship. Their value at date of death forms part of the deceased's estate for IHT purposes.

Missing the deadline

A six-month deadline sounds generous but gathering valuations, locating documents, and completing the forms can take considerable time. Start the process as soon as practicable after death to avoid interest charges.