Help with the IHT400 Form

The IHT400 is the full inheritance tax account for an estate. It is the most detailed form in the probate process, and for many executors it is the point at which administering an estate stops being paperwork and becomes tax work.

This guide explains what the IHT400 form is, what it contains, which schedules go with it, how to submit it, and where executors most often go wrong. It covers England and Wales.

What is the IHT400 form?

IHT400 is the inheritance tax account: a full return of everything the deceased owned and owed, sent to HMRC. It is not a summary. It reports the value of every asset and liability, every lifetime gift, and every relief or exemption being claimed, and it carries a signed declaration from the personal representatives.

You need it where there is inheritance tax to pay, or where there is no tax to pay but the estate does not qualify as an excepted estate. That second limb catches people out: a large estate passing entirely to a surviving spouse may have no tax at all and still need a full IHT400. Our guides on whether you need to complete IHT400 before applying for probate and on excepted estates set out the test in detail.

The form applies to deaths on or after 18 March 1986. For deaths on or before 31 December 2021 the old excepted estate rules and forms IHT205 and IHT207 may apply instead, so check the date of death rather than the date you are applying.

IHT400 guidance notes, and using the current version

HMRC publishes the form alongside a substantial set of IHT400 guidance notes, running to around 95 pages, which work through the form box by box. There is also a separate rates and tables document and a helpsheet for working out interest.

One practical point worth more than it sounds: download a fresh copy of the form and notes each time rather than reusing a saved PDF. HMRC reissues the IHT400 frequently, and the 2026 reforms have added new boxes and a new schedule. Working from last year’s version is a common cause of avoidable rejection.

What the IHT400 form covers

The form itself runs to roughly 19 pages and works through the estate in a fixed order:

• Details of the deceased, and contact details for whoever is dealing with the estate
• The will, and any items referred to in the will but not in the estate
• Which schedules you are attaching
• The estate in the UK, asset category by asset category
• Deductions, being debts and liabilities up to the date of death and the funeral account
• Exemptions and reliefs
• Other assets taken into account to calculate the tax, such as gifts and trust interests
• Working out the inheritance tax, including whether any of it is being paid by instalments
• A simple inheritance tax calculation, for straightforward estates
• The Direct Payment Scheme election
• The declaration, signed by all the personal representatives
• A checklist and the return address

There is also a section asking whether you want the acknowledgement and probate code sent by email. It is worth completing, because it is faster than waiting for the letter.

The IHT400 schedules: which ones you need

The IHT400 is the core form, and the detail sits in supplementary schedules. Using the wrong set is one of the most common problems executors run into, so here is the current list.

Schedule	What it covers	When you need it
IHT402	Claim to transfer unused nil rate band	Claiming unused nil rate band from a spouse or civil partner who died first
IHT403	Gifts and other transfers of value	Any gift or transfer of value since 18 March 1986, including gifts with reservation
IHT404	Jointly owned assets	Anything owned jointly, including assets passing by survivorship
IHT405	Houses, land, buildings and interests in land	UK land and property in the deceased’s sole name
IHT406	Bank and building society accounts	Accounts and NS&I products in the sole name
IHT407	Household and personal goods	Furniture, jewellery, vehicles and personal effects
IHT408	Household and personal goods donated to charity	Where beneficiaries donate goods to charity and claim the exemption
IHT409	Pensions	Any pension provision other than the State Pension, including lump sum death benefits
IHT410	Life assurance and annuities	Life policies, annuities and investment bonds
IHT411	Listed stocks and shares	Quoted holdings that are not a control holding
IHT412	Unlisted stocks and shares and control holdings	Unlisted and AIM shares, and controlling holdings
IHT413	Business and partnership interests and assets	Claiming Business Relief
IHT414	Agricultural Relief	Claiming Agricultural Relief on a farm or farmland
IHT415	Interest in another estate	The deceased was entitled to something from an estate not yet administered
IHT416	Debts due to the estate	Money owed to the deceased
IHT417	Foreign assets	Assets situated outside the UK
IHT418	Assets held in trust	The deceased had a beneficial interest in settled property
IHT419	Debts owed by the deceased	Loans and liabilities, particularly to family or trustees
IHT420	National Heritage assets and conditional exemption	Heritage property and maintenance funds
IHT430	Reduced rate of inheritance tax	Claiming the 36% rate where at least 10% of the net estate goes to charity
IHT435	Claim the residence nil rate band	A qualifying home passes to direct descendants: see the residence nil rate band
IHT436	Claim transferable residence nil rate band	Claiming unused residence nil rate band from a predeceased spouse
IHT437	Claim unused allowance for agricultural or business property relief	Claiming a predeceased spouse’s unused 100% relief allowance under the April 2026 reforms

Two further forms sit alongside these. IHT401a covers a deceased person who was not a long-term UK resident, and replaced IHT401 for deaths on or after 6 April 2025, though IHT401 remains in use for older events. IHT422 is used to apply for an inheritance tax reference, and IHT423 for the Direct Payment Scheme.

A word on numbering, because incorrect lists circulate widely. The series runs IHT401, IHT401a, then IHT402 to IHT423, then jumps to IHT430, then IHT435, IHT436 and IHT437. There is no IHT424 through IHT429, and no IHT431 through IHT434. If a checklist tells you to complete one of those, it is wrong.

The IHT400 Calculation form

The IHT400 itself contains a simple calculation, which is adequate for straightforward estates. Where it is not, you use the separate IHT400 Calculation, an eight-page working sheet.

You will generally need it where the estate involves chargeable lifetime transfers and taper relief, successive charges relief, double taxation relief, an instalment election that splits the tax, the 36% reduced charity rate, or grossing up.

There is a third option that is easy to miss: you can ask HMRC to calculate the tax for you, leaving both the simple calculation and the IHT400 Calculation blank. For an executor without professional help and an estate that is anything other than simple, that is often the sensible choice.

Can you submit the IHT400 online?

No. As things stand, the IHT400 is a postal form. HMRC publishes it as a fillable PDF, but you print it, all the personal representatives sign it by hand, and you post it. GOV.UK’s instruction is to download the form and send it to the address on the form, and there is no digital filing service for it.

The confusion is understandable, because three adjacent things are online:

• Applying for the inheritance tax reference number can be done online
• Paying the tax can be done online, by bank transfer or by approving a payment through your bank
• The probate application itself is online

So an executor can reasonably assume the account is online too. It is not. The probate application depends on a code that HMRC only issues once it has processed the posted IHT400.

The return address is Inheritance Tax, HM Revenue and Customs, BX9 1HT. Keep a complete copy of everything you send.

Getting an inheritance tax reference number first

If there is tax to pay, you need an inheritance tax reference number before you send the form. HMRC asks you to apply at least three weeks before you plan to make the payment, so this needs doing early rather than at the point you are ready to post.

You can apply online, or by posting form IHT422. No reference is needed where there is no tax to pay.

Paying the tax

Inheritance tax is generally due by the end of the sixth month after the month of death, and in most cases it has to be paid before probate is granted. That creates the familiar problem: you need the money in the estate to pay the tax, but you cannot reach it without the grant.

There are several ways through it.

The Direct Payment Scheme. Form IHT423 lets participating banks, building societies and investment providers transfer funds from the deceased’s accounts straight to HMRC. You need a separate IHT423 for each institution.

Instalments. Tax on assets that take time to sell can be paid in ten equal annual instalments. That covers land and buildings, a business or an interest in one, controlling shareholdings, certain unlisted shares, and any asset qualifying for Agricultural or Business Relief. The first instalment is due on the ordinary payment date. Interest normally runs on the outstanding balance, but for deaths on or after 6 April 2026 the instalments are interest-free where the asset qualifies for Agricultural or Business Relief.

British Government Stock. Where the deceased held gilts, these can be used to pay the tax directly, though the transfer can take up to four weeks, so it is not a route to choose if you need probate quickly.

Personal funds. Executors and beneficiaries sometimes pay from their own money or borrow, and recover the amount from the estate once the grant is issued. This is a practical workaround rather than an HMRC scheme, and worth taking advice on before committing your own money.

You can also make payments on account before the final figure is settled, which limits the interest running against the estate.

Deadlines, interest and penalties

Two deadlines apply, and HMRC identifies confusing them as a risk in its own guidance.

The account must be delivered within 12 months of the end of the month in which the person died, or within three months of first acting as personal representative if that is later.

The tax is due earlier, by the end of the sixth month after the month of death. Interest runs from the first day of the seventh month. The late payment rate has moved several times recently and stood at 7.75% from 9 January 2026, so check the current figure rather than relying on a number in an article.

Late delivery of the account attracts an initial £100 penalty, with a further £100 if it is between six and twelve months late, each capped at the tax due. Beyond twelve months there is an additional penalty of up to £3,000, scaled by the amount of tax at stake, and that one is not capped by the tax on the account.

The code for your probate application

Once HMRC has processed the IHT400, it issues a unique code. You enter that code in the probate application, and you cannot submit the application without it.

Expect to wait. HMRC normally issues the code within 20 working days of receiving the IHT400 or the payment, whichever is later. Executors routinely underestimate the probate timetable because they do not allow for this.

This replaced the old IHT421 probate summary for England and Wales in January 2024. IHT421 is still used in Northern Ireland, and Scotland uses form C1 for confirmation. If you are following older guidance that tells you to wait for an IHT421, it no longer applies here.

Where executors go wrong on the IHT400

HMRC publishes an inheritance tax toolkit setting out the areas it sees fail most often. The pattern is consistent.

Valuations. HMRC describes this as the single biggest area of risk. Recurring problems include not using a qualified independent valuer, not giving the valuer full information such as development potential or tenancies, valuing a farm as one block rather than separating dwellings, outbuildings and land, and giving a life policy’s surrender value rather than its open market value at death. Self-valuation is really only safe for ordinary household goods and second-hand cars. Our guide to valuing an estate for probate goes into this further.

Omitted gifts. Lifetime transfers in the seven years before death are frequently left off. HMRC specifically names sales to family at an undervalue, debts written off, mismatched contributions to jointly bought assets, and transfers into trust. Gifts with reservation of benefit are missed almost as a rule, and they are valued at the date of death however long ago they were made, so the seven year rule does not rescue them. HMRC suggests checking bank statements across the full seven years.

Joint assets. Assets passing by survivorship are often left out or reported incompletely on IHT404. Joint bank accounts held purely for convenience are missed entirely.

Missing or incomplete schedules. HMRC names IHT404, IHT413 and IHT414 as the ones most often incomplete, and says this triggers compliance checks.

Reliefs assumed rather than established. Business and Agricultural Relief are conditional, and assuming they apply, misunderstanding the qualifying ownership period, or valuing the business interest wrongly can lead to a claim being refused outright. Property and tax questions often surface here too.

Other recurring errors. Charities and other exempt beneficiaries overlooked; foreign assets not reported; pension death benefits left off IHT409; the predeceased spouse never researched, so the transferable nil rate band is missed or miscalculated; and unsigned declarations, because every personal representative has to sign.

The declaration, and what you are taking on

The declaration on the IHT400 is not a formality. You are confirming that the information is correct and complete, and that you have made the fullest enquiries that are reasonably practicable to establish the open market value of everything in the account.

That is an active duty to investigate, not simply to write down what the family tells you. The form states that you may face financial penalties if the account is delivered late, contains false information, or is not corrected within a reasonable time, and that deliberate concealment can lead to prosecution.

Personal representatives remain personally exposed, and instructing an agent does not by itself remove that exposure. Executors who want certainty before distributing can apply for a clearance certificate on form IHT30.

What is changing

Two changes matter for anyone completing an IHT400 now.

Business and Agricultural Relief, from 6 April 2026. Relief at 100% is limited to £2.5 million of combined qualifying agricultural and business property, with the excess relieved at 50%. The allowance is transferable between spouses and civil partners, so a couple can have up to £5 million. Relief on certain unlisted shares, including AIM holdings, has dropped from 100% to 50%. This is what the new IHT437 schedule is for. Be careful with older summaries: the original proposal was a £1 million non-transferable allowance, and some guidance still reflects that.

Pensions, from 6 April 2027. Most unused pension funds and death benefits will come within the estate for inheritance tax. Personal representatives, rather than scheme administrators, will be responsible for reporting and paying the tax on them, with a mechanism for directing the scheme to pay it. Death in service benefits from a registered scheme and dependants’ scheme pensions are outside the change.

Get help with the IHT400

The IHT400 assumes a working knowledge of inheritance tax that most executors have no reason to have. Getting it wrong can mean HMRC enquiries, delays to probate, additional tax and interest, and personal liability.

Through The Probate Network you can:

• Request a probate quote based on the complexity of your estate
• Book a complimentary consultation with an experienced probate solicitor

There is no obligation, just clear advice before decisions are made that are difficult to unwind. The IHT400 is not a form to rush.

Frequently asked questions

Can you submit the IHT400 online?

No. The IHT400 is a fillable PDF that has to be printed, signed by all the personal representatives and posted to HMRC at BX9 1HT. There is no online filing service for it. Applying for the inheritance tax reference, paying the tax and applying for probate can all be done online, which is why people assume the account can be too.

What are the IHT400 guidance notes?

They are HMRC’s official instructions for completing the form, running to around 95 pages and working through it box by box. There is also a rates and tables document and a helpsheet for calculating interest. Download them fresh alongside the form, because HMRC reissues both regularly.

How long does HMRC take to process the IHT400?

HMRC normally issues the unique code you need for the probate application within 20 working days of receiving the IHT400 or the tax payment, whichever is later. You cannot submit the probate application until that code arrives, so build the wait into your timetable.

Do I need to complete every IHT400 schedule?

No. You complete only the schedules relevant to the estate, and the IHT400 itself asks a series of questions to identify which those are. Completing unnecessary schedules causes as many problems as omitting required ones, because inconsistent figures across forms are a common trigger for HMRC queries.

What happens if I make a mistake on the IHT400?

Tell HMRC as soon as you realise. The declaration requires you to correct anything materially incorrect within a reasonable time, and correcting an error yourself is treated very differently from HMRC finding it. Where values change after submission, a corrective account is the normal route.

Is there tax to pay before probate is granted?

Usually, yes, where the estate is taxable. Inheritance tax is due by the end of the sixth month after the month of death, and HMRC will not issue the code you need for the probate application until the tax has been paid or an instalment arrangement is in place. The Direct Payment Scheme exists to let you pay from the deceased’s own accounts before the grant.

This article is for general guidance only and does not constitute legal, tax or financial advice. Rules and thresholds can change and every estate is different. For advice on your own circumstances, speak to a qualified professional. You can book a free legal consultation through The Probate Network.