How to Fill In Form IHT400: A Box-by-Box Worked Example for a £650,000 Estate
To fill in form IHT400 you work from the supplementary schedules inwards: value each asset on its own schedule (the house on IHT405, accounts on IHT406, joint assets on IHT404), tick those schedules on page 3, carry the totals onto the main form, then run the Calculation pages to apply the £325,000 nil-rate band and up to £175,000 residence nil-rate band before charging 40% on the balance. You only need IHT400 at all when Inheritance Tax is payable or the estate is not an "excepted estate" — otherwise you report values on the probate application instead.
First decide: simple route or full IHT400
Before touching a single box, confirm you actually need IHT400. For most deaths on or after 1 January 2022, an estate that owes no tax and meets the "excepted estate" limits is reported directly on the probate application — there is no IHT400 to file. You complete the full IHT400 when Inheritance Tax is due, or when the estate fails the excepted-estate conditions (for example, foreign assets above the limit, large gifts in the seven years before death, or certain trusts). See HMRC's guidance on checking the type of estate and the IHT400 form and notes.
Our worked example below is a genuinely taxpaying estate, so IHT400 is required.
The order to work in (schedules first, main form second)
IHT400 is a hub: the figures in its boxes nearly all come from the supplementary schedules. So the practical order is:
- Open IHT400 and fill in the deceased's details on pages 1–2.
- Work out which schedules you need, complete each one, and value the assets there.
- Tick those schedules on the Schedules checklist, page 3.
- Carry each schedule total into the matching box on IHT400 pages 6–10 (assets) and the deductions pages.
- Run the Calculation to work out the tax.
- Sign and date the declaration on page 14, enclose every ticked schedule, and pay the tax.
Meet the estate: Margaret
Worked example — the estate of Margaret
Margaret, a widow, died in January 2026. She left everything to her two children. Her estate:
| Asset | Value | Schedule |
|---|---|---|
| Her home (sole name), passing to her children | £420,000 | IHT405 |
| Current & savings accounts, NS&I | £180,000 | IHT406 |
| Joint savings account with her sister (Margaret's half) | £40,000 | IHT404 |
| Small pension lump sum & household contents | £10,000 | IHT400 main form |
| Gross estate | £650,000 | — |
No mortgage; funeral costs of £4,000 are deducted later. This example keeps it simple — a real pension lump sum may sit outside the estate depending on the scheme rules, so always check the scheme.
Picking the right supplementary schedules
Each asset type has its own form. For Margaret:
| Schedule | What it covers | In this estate |
|---|---|---|
| IHT405 | Houses, land and buildings owned by the deceased | The £420,000 home |
| IHT406 | Bank & building society accounts, National Savings, Premium Bonds | The £180,000 of accounts |
| IHT404 | Assets owned jointly with another person | Margaret's £40,000 half of the joint account |
There are many more schedules (IHT402 to transfer an unused spouse's nil-rate band, IHT435 for the residence nil-rate band, IHT403 for gifts, and so on). For Margaret you would also use IHT435 to claim the residence nil-rate band because the home passes to her children, and IHT402 to claim her late husband's unused nil-rate band if it is available. The full list lives on HMRC's Inheritance Tax forms collection.
Tick the Schedules checklist on page 3
Page 3 of IHT400 has a list of every schedule with a "yes" box. This is not optional housekeeping — HMRC uses it to check that every form you reference is actually enclosed. Tick IHT404, IHT405 and IHT406 (and IHT435 / IHT402 if claiming the extra bands). A missing tick, or a ticked schedule that you forgot to enclose, is one of the most common reasons an account is sent back.
Carrying the figures onto the IHT400 boxes
Once each schedule is valued, its total flows into the matching box on the main form's asset pages (broadly pages 6–10). In outline:
| IHT400 area | Comes from | Margaret |
|---|---|---|
| Jointly owned assets | IHT404 total | £40,000 |
| Deceased's own assets — property | IHT405 total | £420,000 |
| Deceased's own assets — bank & NS&I | IHT406 total | £180,000 |
| Other assets (pension lump sum, contents) | IHT400 main form | £10,000 |
| Liabilities & funeral expenses | IHT400 deductions pages | £4,000 funeral |
Add the assets to get the gross estate of £650,000, then subtract allowable deductions (here, the £4,000 funeral) to reach the net estate of £646,000. Both of those numbers matter later — they are exactly the figures HMRC will quote back to you for the probate application.
The Calculation pages: turning values into a tax figure
IHT400 has a dedicated Calculation section where the tax is worked out. The mechanics, using HMRC's current frozen thresholds, are:
- Nil-rate band: £325,000, frozen since 2009 and held to 5 April 2031 (HMRC rates & allowances).
- Residence nil-rate band (RNRB): up to £175,000 when a home passes to direct descendants — frozen to 5 April 2030 (HMRC RNRB guidance). Claimed via IHT435.
- Standard rate: 40% on the value above the available bands (gov.uk/inheritance-tax).
Worked example — Margaret's tax calculation
| Step | Figure |
|---|---|
| Net estate | £646,000 |
| Less nil-rate band | − £325,000 |
| Less residence nil-rate band (home to children) | − £175,000 |
| Taxable balance | £146,000 |
| Inheritance Tax at 40% | £58,400 |
If we ignore the funeral deduction and use the round £650,000 gross figure, the balance is £150,000 and the tax is £60,000 — the headline number most people picture. The point is the same: the two bands shelter £500,000, and only what sits above is charged.
If Margaret's late husband had died leaving everything to her, his unused nil-rate band (and possibly his RNRB) could be transferred via IHT402/IHT436, lifting the combined threshold to as much as £1,000,000 — which would wipe out the tax entirely. That is why claiming the transferable bands is worth the extra schedule.
What happens after you submit (the post-17-January-2024 process)
This is the part that has changed and trips people up. Since 17 January 2024, in England and Wales you no longer complete or send form IHT421 (the old "probate summary") with your IHT400. Instead:
- You send the completed IHT400 and schedules to HMRC and pay the tax.
- HMRC processes it and sends you a letter containing a unique code plus the gross and net estate values.
- You enter that code and those values into the online probate application at HM Courts & Tribunals Service before applying for the grant.
HMRC advises waiting for that letter before submitting the probate application, and warns it can take time after the IHT400 is received. The change applies to England and Wales only — Scotland and Northern Ireland keep their existing process. See STEP's summary of the revised probate procedure.
Common errors that cause delays
| Error | Why it bites | Fix |
|---|---|---|
| Not signing & dating page 14 | The declaration is the legal heart of the account; HMRC returns unsigned forms | Every personal representative signs and dates the page 14 declaration |
| Missing the 12-month filing window | IHT400 must be delivered within 12 months of the end of the month of death; penalties can follow | Diarise the date of death + 12 months as a hard backstop |
| Missing the 6-month payment deadline | Tax is due by the end of the sixth month after death | Pay the tax due before or with the IHT400 — see gov.uk/paying-inheritance-tax |
| Interest on tax paid late | HMRC charges interest from the due date until paid, even while you wait for the grant | Pay early; consider the instalment option for property, and the direct-payment scheme from the deceased's bank |
| Ticked schedules not enclosed | Page 3 says a schedule applies but it is not in the envelope | Cross-check page 3 ticks against the physical bundle before posting |
On Margaret's January 2026 death, tax of roughly £58,400 should be paid by 31 July 2026 (end of the sixth month). Pay after that and interest accrues; the IHT400 itself can be delivered up to the end of January 2027, but leaving the tax unpaid that long is an expensive mistake.
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Frequently asked questions
Do I need to fill in the full IHT400, or is there a simpler form?
You only complete IHT400 if the estate is taxpaying or otherwise does not qualify as an "excepted estate". For most deaths on or after 1 January 2022 where no tax is due and the estate is within the limits, you report values directly on the probate application instead of filing IHT400. IHT400 is the full account used when Inheritance Tax is payable or the excepted-estate conditions are not met.
Which IHT400 schedules do I need for a house, bank accounts and a joint asset?
Use IHT405 for land and buildings (the house), IHT406 for bank and building society accounts, National Savings and Premium Bonds, and IHT404 for assets owned jointly with another person. Tick each one on the Schedules checklist on page 3 of IHT400 and send them in with the main form.
How much Inheritance Tax is due on a £650,000 estate left to children?
If a single person leaves a £650,000 estate including a home passing to their children, the nil-rate band of £325,000 plus the residence nil-rate band of up to £175,000 can shelter £500,000. Tax at 40% then applies to the remaining £150,000, giving £60,000. Transferred bands from a late spouse can reduce or remove this — every estate differs, so check your own figures.
What is the HMRC unique code and why do I need it?
Since 17 January 2024, in England and Wales you no longer send form IHT421 with your IHT400. After HMRC processes your IHT400 it sends a letter with a unique code plus the gross and net estate values. You enter that code and those values into the online probate application before applying for the grant.
When does the Inheritance Tax have to be paid?
Inheritance Tax is due by the end of the sixth month after the month in which the person died — for a January death, that is 31 July. HMRC charges interest on tax paid after that date, so pay the tax due before, or at the same time as, sending in IHT400.
What are the most common IHT400 mistakes?
The biggest are forgetting to sign and date the declaration on page 14, missing the 12-month filing window and the six-month payment deadline, not enclosing every schedule ticked on page 3, and arithmetic slips on the Calculation pages. A signed, dated, fully-enclosed account avoids most HMRC queries.
Pay the tax: end of the 6th month after death. File IHT400: 12 months after the end of the month of death.
IHT400 → HMRC → unique code + values → online probate application. No IHT421 in England & Wales.
General information, not personal United Kingdom tax/legal advice. Verify with a qualified professional.
Sources: gov.uk/inheritance-tax, HMRC Inheritance Tax thresholds & interest rates, HMRC residence nil-rate band guidance, gov.uk/paying-inheritance-tax, IHT400 form & notes, and STEP: revised probate procedure (17 Jan 2024). Figures verified against gov.uk on 2026-06-03.