IHT400 Form: Who Needs It and How to Complete It
The IHT400 is HMRC's full inheritance tax return — the form executors must complete for most estates that owe or could owe IHT. It is notoriously long, with dozens of supplementary schedules. Here is who needs it, what it covers, and how to work through it systematically.
Note: This article covers the IHT400 process in England and Wales. Scotland uses form C1 (and C5 for the full IHT account) but the underlying tax calculations are the same. Forms and processes may change — always check GOV.UK for the latest versions.
IHT400 at a Glance
What Is the IHT400?
The IHT400 is HMRC's inheritance tax account — a comprehensive return that details everything the deceased owned, owed, and gave away. It is used to calculate the inheritance tax due on the estate.
The form itself runs to around 16 pages, but most estates will also need several supplementary schedules (IHT401 to IHT436) covering specific types of asset, relief, or exemption. Together, these can easily reach 50+ pages for a moderately complex estate.
On completion, HMRC uses the IHT400 to:
- Calculate the IHT due (or confirm none is payable)
- Issue the IHT421 certificate, which the executor needs to apply for probate
- Decide whether to open an enquiry into the estate's values or reliefs claimed
IHT400 vs IHT205: Which Do You Need?
Not all estates need the full IHT400. Smaller, simpler estates may qualify to use the shorter excepted estate process. The key question is whether the estate is an “excepted estate” — one that meets certain conditions allowing a simplified return.
| Condition | IHT205 / Excepted | IHT400 required |
|---|---|---|
| Estate below NRB (£325,000) | Usually yes | No (if no other factors) |
| Estate below NRB + RNRB + transferable bands | May qualify | Check conditions |
| IHT is payable | No | Yes |
| Gifts over £250,000 in last 7 years | No | Yes |
| Trust interests | No | Yes |
| Foreign assets over £100,000 | No | Yes |
| Claiming BPR or APR | Depends | Usually yes |
Simplified decision guide — always check the full excepted estate conditions
The excepted estate rules changed in January 2022 and the thresholds were raised significantly. Many estates that would previously have needed an IHT400 now qualify as excepted. Check the latest conditions on GOV.UK before deciding which form to use.
Key Sections of the IHT400
The IHT400 is divided into several main sections:
| Section | What it covers | Key information needed |
|---|---|---|
| Personal details | Deceased's name, address, date of death, domicile | Death certificate, personal records |
| Will and distribution | Whether there is a will, who inherits | Will, any codicils |
| Assets in the UK | Property, bank accounts, investments, personal possessions | Valuations, bank statements, share certificates |
| Assets outside the UK | Foreign property, overseas bank accounts | Valuations in sterling |
| Debts and liabilities | Mortgages, loans, outstanding bills, funeral costs | Loan statements, invoices |
| Exemptions and reliefs | Spouse exemption, charity, BPR, APR | Evidence of qualifying conditions |
| Gifts in last 7 years | PETs and CLTs | Gift records, bank statements |
| Trusts | Interests in trusts | Trust deeds, valuations |
| Tax calculation | Working out the IHT due | All of the above |
John dies in June 2026 leaving a home worth £400,000, savings of £200,000, and investments of £150,000 to his two adult children. He was widowed.
| IHT400 section | Value |
|---|---|
| Property (IHT405) | £400,000 |
| Bank accounts (IHT406) | £200,000 |
| Investments | £150,000 |
| Gross estate | £750,000 |
| Less: funeral costs and debts | −£8,000 |
| Net estate | £742,000 |
| Less: NRB (own + transferred) | −£650,000 |
| Less: RNRB (own + transferred) | −£92,000 (tapered — estate below £2M) |
| Taxable estate | £0 |
| IHT due | £0 |
John's estate uses both his own and his late wife's transferred NRB (£650,000 total) plus partial RNRB. The executors still need to file the IHT400 to claim the transferred allowances, even though no IHT is due.
Supplementary Schedules
You only need to complete the supplementary forms that apply to the estate. Here are the most commonly used ones:
Asset Schedules
| Form | Purpose | When needed |
|---|---|---|
| IHT403 | Gifts and other transfers of value | Gifts over £3,000/year in last 7 years, or claiming normal expenditure from income |
| IHT404 | Jointly owned assets | Any assets owned as joint tenants or tenants in common |
| IHT405 | Houses, land, buildings and interests in land | Any property in the estate |
| IHT406 | Bank and building society accounts | Accounts totalling over £5,000 |
| IHT407 | Household and personal goods | Items worth over £500 individually |
| IHT408 | Household and personal goods donated to charity | If claiming charity exemption on goods |
| IHT409 | Pensions | Any pension benefits, lump sums or annuities |
| IHT410 | Life insurance and annuities | Any life policies or annuity contracts |
Relief and Exemption Schedules
| Form | Purpose | When needed |
|---|---|---|
| IHT400 (pages 11-12) | Business property relief (BPR) | Business interests, unquoted shares, farmland used in business |
| IHT400 (pages 11-12) | Agricultural property relief (APR) | Agricultural land and farm buildings |
| IHT435 | Claim RNRB | Leaving home to direct descendants |
| IHT436 | Claim transferred RNRB | Surviving spouse claiming deceased spouse's unused RNRB |
| IHT401 | Domicile outside England and Wales | Deceased not domiciled in England/Wales |
| IHT402 | Claim transferred NRB | Surviving spouse claiming deceased spouse's unused NRB |
For a full list, check the IHT planning checklist which maps estate circumstances to the relevant forms.
HMRC Reference and Payment Process
The IHT400 and payment process work together:
- Get an IHT reference number: Apply using form IHT422 at least 15 working days before you want to pay. You need this reference for all payments.
- Complete the IHT400 and supplementary forms: Gather all asset valuations, gift records, and supporting evidence.
- Pay the IHT due: Using the Direct Payment Scheme, bank transfer, or other method. See our guide on how to pay inheritance tax for full details.
- Submit the IHT400: Send the completed form and supplementary schedules to HMRC.
- Receive IHT421: HMRC processes the return and issues the IHT421 certificate (usually 15-20 working days).
- Apply for probate: Use the IHT421 as part of your probate application.
Tip: You can pay the IHT and submit the IHT400 at the same time. Do not wait for HMRC to process the form before paying — the payment deadline is 6 months after death regardless of when the form is processed.
How Estate Map Helps
While Estate Map does not generate the IHT400 form itself, it can significantly streamline the preparation:
- Calculate your IHT liability: Enter estate details into the calculator and see exactly how much IHT is due, including all available reliefs and allowances
- Identify relevant reliefs: The calculator automatically applies NRB, RNRB, spouse exemption, BPR, APR, and charity relief where applicable
- Understand the 2026 reform impact: See how the APR/BPR cap affects your estate
- Model scenarios: Try different planning approaches to see how they change the IHT bill before committing to action
Having your IHT calculation ready before starting the IHT400 gives you confidence in the numbers and helps you identify which supplementary forms you will need.
Frequently Asked Questions
When do I need to file an IHT400?
You need to file an IHT400 if the estate is above the IHT threshold (taking into account all assets, gifts in the previous 7 years, and trust interests), if the deceased owned foreign assets worth over £100,000, or if the estate does not qualify for the simplified IHT205/IHT217 forms. In practice, most estates worth over £325,000 will need an IHT400.
What is the difference between IHT400 and IHT205?
The IHT205 (or its replacement, the excepted estate form) is a shorter, simpler return for estates that fall below the IHT threshold and meet certain conditions. The IHT400 is the full inheritance tax return required for larger or more complex estates. If IHT is payable, you must use the IHT400.
How long does it take HMRC to process an IHT400?
HMRC typically takes 15-20 working days to process an IHT400 and issue the IHT421 certificate (needed for the probate application). Complex cases or those selected for enquiry can take significantly longer. You can track progress by calling the HMRC IHT helpline.
Do I need a solicitor to complete the IHT400?
No, executors can complete the IHT400 themselves. However, for complex estates involving business assets, trusts, foreign property, or multiple reliefs, professional help from a solicitor or probate specialist is strongly recommended. Errors can lead to over- or under-payment of tax and potential HMRC enquiries.
What supplementary forms do I need with the IHT400?
The supplementary forms depend on the estate's assets. Common ones include IHT403 (gifts), IHT404 (jointly owned assets), IHT405 (houses and land), IHT406 (bank accounts), IHT407 (household goods), IHT409 (pensions), IHT410 (life insurance), and IHT435/IHT436 (claiming RNRB and transferred RNRB).
Can I amend an IHT400 after submitting it?
Yes. If you discover errors or asset values change, you can write to HMRC to correct the return. If assets sell for less than the probate value, you may be able to claim a refund using form IHT35 (property) or IHT38 (shares). There is a 12-month 'correction period' after the grant of probate where you should notify HMRC of any changes.
Calculate Your IHT Before Starting the IHT400
Use Estate Map to work out the inheritance tax due on the estate. Having accurate figures ready makes completing the IHT400 faster and reduces the risk of errors.
Calculate IHT now →