The IHT400 is the full inheritance tax account. It is a core form of numbered boxes plus supplementary schedules, one for each type of asset, gift, debt or relief, and it must reach HMRC within 12 months of the end of the month of death and before the executors apply for probate. Most errors come from missing lifetime gifts, wrong valuations, debts that are never repaid and changes that are never reported.

When do executors need an IHT400 rather than the probate form?

GOV.UK says the IHT400 is needed if there is inheritance tax to pay or the estate is not an excepted estate. That includes estates with no tax due that fail an excepted estate condition, for example gifts over £250,000 in the seven years before death, an estate over £3 million, or foreign assets over £100,000. Check excepted estates first. IHTA 1984 section 216(6) sets the deadline at 12 months from the end of the month of death, or three months from when the personal representatives first act if later. Apply for an inheritance tax reference number at least three weeks before sending the form.

How is the form laid out?

The box numbers, taken from the current form and HMRC’s IHT400 notes, follow the order you work in:

Boxes What they cover
1 to 28 Deceased’s details, contact and repayment details, the will
29 to 48 Yes or no questions that tell you which schedules to complete
49 to 79 UK assets, split into column A and column B, ending with the gross UK estate
80 to 91 Debts, funeral expenses and the net UK estate
92 to 108 Exemptions and reliefs, foreign assets, other assets taken into account such as gifts and trusts, and the total chargeable estate
109 to 119 The 36% reduced rate question, the instalment election and the simple tax calculation
120 and 121 Direct Payment Scheme and the declaration

Column A holds assets whose tax must be paid before the grant. Column B holds assets, such as property and businesses, whose tax can be paid by instalments. Box 110 records whether you want to use that option; see paying inheritance tax by instalments. If the simple calculation in boxes 111 to 119 does not fit, for example where relief, lifetime gifts or the residence nil rate band are involved, the separate IHT400 Calculation worksheet is used, or HMRC will work out the tax.

Which schedules apply?

Questions 29 to 48 point to the schedules. The main ones are:

  • IHT402 and IHT436: transfer of a late spouse’s unused nil rate band and residence nil rate band; IHT435 claims the residence nil rate band itself;
  • IHT437: transfer of a late spouse’s unused 100% relief allowance for agricultural or business property;
  • IHT403: lifetime gifts and other transfers of value;
  • IHT404: jointly owned assets; IHT405: houses, buildings and other property interests;
  • IHT406: bank and building society accounts, National Savings and Premium Bonds;
  • IHT407 and IHT408: household and personal goods, and goods donated to charity;
  • IHT409: pensions; IHT410: life assurance and annuities;
  • IHT411 and IHT412: listed shares, and unlisted shares or control holdings;
  • IHT413 and IHT414: business relief and agricultural relief;
  • IHT415 to IHT419: interests in another estate, debts due to the estate, foreign assets, trusts, and debts owed by the deceased;
  • IHT420, IHT430 and IHT401: heritage assets, the 36% reduced rate for charitable estates, and domicile outside the UK.

The IHT400 notes say IHT435 and IHT436 are completed last, after box 108, because they depend on the figures already entered. In Northern Ireland, IHT421 goes with the IHT400, and IHT423 is the Direct Payment Scheme schedule sent to each bank.

Can executors send a reduced IHT400?

Yes, where little or no tax is due because most of the estate passes to a spouse, civil partner, qualifying charity or national body. The notes require the deceased to have been long term UK resident, and the gross value of everything not passing to exempt beneficiaries (including joint assets, gifts in the last seven years, gifts with reservation and foreign assets outside the will) to be within the nil rate band, plus any transferred band. Boxes 1 to 28 are completed in full and every question from 29 to 48 answered, but some schedules can be skipped where all the assets pass to exempt beneficiaries. Exempt assets still need an open market estimate, not a nominal figure. A residue split between a spouse and children needs the full form.

How should assets be valued?

The notes require open market value at the date of death, with assets rounded down and liabilities rounded up to the nearest pound. GOV.UK suggests an estate agent or chartered surveyor for property and a professional valuation for anything worth over £1,500, while ordinary household goods can be estimated. Where one or two figures are not yet known, such as an income tax repayment, a provisional estimate is allowed if listed at box 121 and corrected later. Cryptoassets are part of the estate: HMRC’s February 2026 newsletter says to report them in box 76 with details in the additional information section. Inheritance tax values also become the capital gains base cost for beneficiaries, as explained in CGT on death.

What happens after it is sent?

HMRC works out the tax and interest, and the unique code for a probate application in England and Wales usually arrives within 20 working days of the IHT400 or the payment, whichever is later. GOV.UK says that if HMRC has not been in touch within 14 weeks, no further checks will be made. Final values must be reported when known or within 18 months of death, whichever is sooner, and earlier for certain changes such as a sale of property or shares at a loss or a change of more than £50,000. Corrections go on a corrective account. Records should be kept, as HMRC can ask for them up to 20 years after the tax is paid.

What penalties apply?

Under IHTA 1984 section 245, failing to deliver the account brings a £100 penalty, a further £100 if it is still outstanding six months after the deadline, and up to £3,000 if it is outstanding a year after the deadline and tax would have been shown. The fixed penalties cannot exceed the tax due, and a reasonable excuse defence applies; see reasonable excuse. An inaccurate IHT400 falls within the Finance Act 2007 Schedule 24 penalty regime for careless or deliberate errors, as do statements claiming a relief or exemption.

A worked example

Illustration only. Joan’s estate is a £500,000 house, £150,000 in savings and a £20,000 car, left to her two children. She gave her son £40,000 three years before death. The executors complete IHT403 for the gift, IHT405 for the house, IHT406 for the savings, IHT407 for the car and household goods, and IHT435 for the residence nil rate band. The house goes in column B and the rest in column A. Because there is a gift and a residence nil rate band claim, the simple calculation does not fit, so they use the IHT400 Calculation and elect at box 110 to pay the tax on the house by instalments.

What are the most common mistakes?

  • Leaving out lifetime gifts, or regular gifts from income above the annual exemption, which also affect the nil rate band available.
  • Entering the whole value of a jointly owned asset instead of the deceased’s share, or omitting IHT404.
  • Deducting a debt that will not be repaid from the estate. The notes say executors must tell HMRC so the deduction can be disallowed.
  • Giving round number guesses for property or shares without evidence, or not listing provisional figures at box 121.
  • Missing the 24 month time limit for transferable nil rate band claims, which runs from the end of the month of death.
  • Sending the original will. GOV.UK says to send copies of the will and codicils only.
  • Forgetting to report later sales below probate value, which may reduce the tax.

Paying the tax is often the next hurdle; see paying inheritance tax before probate. Accountants acting as executors should also read accountants as executors and trustees.

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Sources

Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 8 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.