IHT400 Form UK: Complete Guide to the Inheritance Tax Return, Schedules, and Excepted Estates (2026)
The IHT400 is the main HMRC inheritance tax return, required before probate can be granted. The most frequently missed items: the transferred NRB (IHT402), gifts history (IHT403), and RNRB claim (IHT435 + IHT436), none of which are automatic.
| Schedule | Title | Purpose & Key Points | When Required |
|---|---|---|---|
| IHT400 | Inheritance Tax Account (main form) | The main return: deceased's personal details; estate summary; IHT calculation; list of all assets and liabilities; election for instalment payment (s227 IHTA); reduced rate (36%) election; declaration signed by all executors | Required for all non-excepted estates; threshold exceeded; complex assets; 7yr gifts above exemptions; any IHT due |
| IHT401 | Domicile outside the UK | Claim non-domicile status; limit estate to UK-situs assets only (s6(1) IHTA 1984). Relevant for non-UK domiciled deceased, or LTUKR test (Finance Act 2025) | Deceased was non-UK domiciled at death; or LTUKR status is in dispute |
| IHT402 | Claim to transfer unused nil rate band | Claim the unused NRB % from a deceased spouse/civil partner to the estate of the second-to-die (s8A IHTA 1984). NOT automatic, must be actively claimed by executors | Deceased had a previously deceased spouse/civil partner who left unused NRB; claim up to 100% additional NRB (£325k in 2026/27) |
| IHT403 | Gifts and other transfers of value | List ALL gifts and transfers of value made by the deceased in the 7 years before death (and earlier for CLTs); claim exemptions (s19 annual; s20 small gifts; s21 normal expenditure from income; s22 wedding; s23 charity); determine which are chargeable PETs or CLTs | Deceased made gifts in 7yr before death (including annual exemption amounts; any gift of £3k+ requires disclosure); s21 claims require income/expenditure evidence |
| IHT405 | Houses, land, buildings, and interests in land | Detail all property (freehold, leasehold, shared ownership); professional RICS open market valuations at date of death; mortgages outstanding (deductible); property occupied by third parties | Deceased owned any property (including partial shares, overseas property, land) |
| IHT411 | Listed stocks and shares | Value listed shares, unit trusts, OEICs, gilts at date of death using the ¼-up rule: value = lower price + ¼ × (higher price − lower price), or the mid-price of bargains on the day, whichever is lower; use Stock Exchange Daily Official List for date of death | Deceased held listed shares, ISA stocks and shares (value on date of death), unit trusts, ETFs, gilts |
| IHT413 | Business or partnership interests | Claim Business Property Relief (BPR, ss103-114 IHTA 1984): 100% BPR on qualifying unincorporated businesses and unquoted shares (including AIM shares held 2yr+); 50% BPR on certain quoted shares and assets used in business. £1m combined BPR/APR cap from April 2026 | Deceased owned a business, partnership interest, unquoted company shares, or AIM shares qualifying for BPR |
| IHT435 | Claim for residence nil rate band (RNRB) | Claim RNRB (s8D IHTA, £175k in 2026/27) where a qualifying residential interest passes to a direct descendant (s8K IHTA); includes downsizing addition (ss8FA-8FE IHTA, claim if home sold/downsize after 8 July 2015) using form LD1 | Deceased owned a home that passes to direct descendants; or downsizing addition is claimed; RNRB is NOT automatic, must be claimed |
| IHT436 | Claim to transfer any unused residence nil rate band | Claim the unused RNRB % from a deceased spouse/civil partner (s8G IHTA 1984), NOT automatic; must be actively claimed. Includes transferred downsizing addition (s8FE IHTA) | Deceased had previously deceased spouse/civil partner who left unused RNRB (e.g., first death had no qualifying home; or home value was below RNRB; or taper applied to reduce RNRB) |
| IHT430 | Reduced rate of inheritance tax | Claim the 36% reduced IHT rate (s36 IHTA 1984) where at least 10% of the 'baseline amount' is left to qualifying charities (registered UK charities); baseline = net estate − NRB − RNRB − other exemptions | Deceased left 10%+ of baseline to charity in will or codicil; HMRC will verify the charity is registered with HMRC; percentage-of-residue legacies recommended |
IHT400: submitted to HMRC Inheritance Tax, Nottingham, before grant of probate. IHT paid (or instalment election s227 IHTA for qualifying assets) before probate. IHT421: issued by HMRC after processing; sent to probate registry; required for PA1P/PA1A application. Processing time: 8-12 weeks typical; longer for complex estates. tNRB (IHT402) and tRNRB (IHT436) NOT automatic, must be claimed; worth up to £325k + £175k per person. RNRB (IHT435) NOT automatic. ¼-up rule (IHT411): listed share value = lower price + ¼ × (higher - lower) at date of death. BPR/APR (IHT413/IHT414): £1m combined cap from April 2026 (Finance Act 2026). 36% reduced rate (IHT430): ≥10% of baseline to registered charity. Excepted estates (no IHT400): estate < £1m AND IHT = £0; use simplified declaration in probate form (since 2022 reforms). Corrective Account: C4 form for post-submission amendments. Penalty regime: Finance Act 2007 Sch 24; 0-100% of understated tax. HMRC enquiry window: 6 years (unlimited for fraud). England and Wales; Scotland: similar form but different processes.
IHT400 Guide: Everything Executors Need to Know
When is the IHT400 required?
The IHT400 is required for any estate that is NOT an 'excepted estate'. An estate qualifies as excepted (simplified route, no IHT400 required) where: (1) Low-value estates: total estate value (before exemptions) is below £1 million AND IHT due is zero (the estate is within the available thresholds including any transferred NRB and RNRB); AND there are no complex assets or significant gifts to report. For example: estate of £450,000 passing entirely to children, with full NRB (£325k) and RNRB (£175k) = excepted estate; no IHT400 required. (2) Exempt estates: the estate passes entirely to the spouse/civil partner (s18 IHTA) or entirely to charity (s23 IHTA), no IHT due regardless of the estate value; no IHT400 required (IHT217 for spouse transfer of NRB). (3) Foreign domicile estates: deceased was non-UK domiciled at death AND was not a Long-Term UK Resident (LTUKR from April 2025); UK estate is below £150,000; and there are no UK assets requiring detailed disclosure. In practice: many larger or more complex estates require an IHT400, including: any estate where IHT is due; estates where the deceased made significant gifts in the 7 years before death (including failed PETs); estates with business interests (BPR claim); estates with foreign assets; estates with trust interests; estates where the NRB needs to be reduced by prior CLTs. The IHT400 must be submitted to HMRC BEFORE the executor applies for a grant of probate. IHT must be paid (or an instalment election made) before the grant is issued.
The most important schedules, tNRB, gifts, and RNRB
Three schedules are critical and frequently overlooked: (1) IHT402, Transferred NRB: The transferred NRB (s8A IHTA 1984) is NOT automatic. The executor must complete IHT402 to claim the unused NRB from each previously deceased spouse or civil partner. Many executors miss this, particularly where the first death was many years ago and paperwork is incomplete. Evidence required: the first spouse's death certificate; grant of probate or letters of administration from the first estate; IHT return (or evidence that no IHT was paid) from the first estate; the marriage/civil partnership certificate. If the IHT400 from the first death cannot be located: use IHT422 application for a clearance letter, or contact HMRC's IHT office with all available evidence. Maximum tNRB: 100% of current NRB (£325,000 in 2026/27), accumulated from multiple prior deceased spouses if applicable. (2) IHT403, Gifts: This is where most IHT errors occur. Executors must list ALL gifts made in the 7 years before death, including small gifts (although s19 and s20 exempt gifts do not need detailed listing for each small cash gift). For significant gifts (any amount that could affect the NRB calculation): exact date; recipient; value; exemptions claimed. Normal expenditure from income (s21 IHTA) claims require: the donor's annual income for each relevant year; annual expenditure; surplus income; pattern of gifting, HMRC IHT403 has specific boxes for s21 claims; back this up with a schedule of income/expenditure prepared by the executors. (3) IHT435 and IHT436, RNRB and transferred RNRB: Like the tNRB, the RNRB and tRNRB are NOT automatic. The executor must actively claim them on IHT435 (RNRB) and IHT436 (tRNRB). For the tRNRB (IHT436): evidence of the first spouse's unused RNRB is required, the grant/estate details from the first death. If there was no qualifying home at the first death and the first death occurred before RNRB was introduced (April 2017), the full unused RNRB percentage (100%) still transfers, even if the first death was in 2005, provided the survivor's death is after April 2017.
How HMRC processes the IHT400 and what happens next
After the executor submits the IHT400 (by post or online): (1) HMRC reviews the return. HMRC's IHT office (HMRC Inheritance Tax) is based in Nottingham. Processing times can be 8-12 weeks or longer for complex estates. HMRC may raise queries, particularly on BPR claims (business property relief), foreign assets, trust interests, and large gift claims. (2) HMRC issues a receipt and the IHT421. The IHT421 is a form sent by HMRC to the probate registry confirming the IHT position. The executor cannot submit the IHT421 themselves, HMRC must issue it. (3) Executor applies for grant of probate: using form PA1P (testate, with will) or PA1A (intestate, without will), submitted to HMCTS Probate Service. The IHT421 is attached to the probate application (or HMRC sends it directly to the probate registry, the executor should check HMRC's process). (4) Grant of probate issued: typically 4-8 weeks after the probate application is submitted with a complete IHT421. The grant enables the executor to: access and close bank accounts; transfer or sell property; pay estate debts; distribute to beneficiaries. (5) Corrective accounts (amendments): if the estate value changes after the IHT400 is submitted (e.g., property sold for more or less than the probate value), the executor submits a Corrective Account (C4 form) to HMRC. Additional IHT becomes payable if the estate value increased; HMRC repays overpaid IHT (with interest) if the estate value decreased. Interest note: HMRC pays interest on overpaid IHT at the HMRC repayment rate (lower than the late payment rate).
Common IHT400 errors and HMRC investigations
The most common IHT400 errors that trigger HMRC queries and penalties: (1) Missing gifts in IHT403: executors often do not have a complete record of the deceased's gifts in the 7 years before death. The solution: bank statement review for the deceased's accounts over the 7-year period; look for regular transfers to family members; enquire of beneficiaries whether they received gifts. (2) Undervalued property: HMRC District Valuer can challenge property valuations. Use a professional RICS 'Red Book' valuation at the date of death. Undervalued property is a common target for HMRC enquiries. The District Valuer typically challenges values where the RICS valuation appears low relative to comparable sales. (3) Incorrect BPR claim: HMRC challenges BPR claims where the business activity is partly or wholly investment (rather than trading). A property rental business, for example, generally does NOT qualify for BPR (investment business exclusion, s105(3) IHTA 1984). Mixed trading/investment businesses require analysis to determine the qualifying proportion. (4) Failure to claim tNRB or tRNRB: many families lose up to £325,000 NRB and £175,000 RNRB per person by failing to claim the transferred amounts. Executors should check whether ANY prior spouse/civil partner is deceased and claim via IHT402 (tNRB) and IHT436 (tRNRB). (5) Excepted estate misclassification: declaring a non-excepted estate as excepted, typically where the estate is below £1m in isolation but the 7-year gift history means the estate SHOULD have filed an IHT400 (CLTs in the 7yr window increase the estate's reporting obligations). HMRC can open an investigation years after probate and impose penalties for underreported estates.
Excepted estates, the simplified route and when it applies
An excepted estate does not require a full IHT400. Instead, a simplified declaration is made on IHT205 (most estates) or IHT207 (foreign domicile cases). From 1 January 2022, HMRC updated the excepted estate thresholds: (1) Low-value estates: the estate is excepted if (a) total estate (including gifts in 7yr, trust interests, and foreign assets) is below £1 million; AND (b) IHT due is zero (all assets within NRB + any transferred NRB + RNRB + exemptions); AND (c) the estate does not involve complex assets (no foreign assets above £100k, no trust interests above £250k, no unlisted shares above £250k). (2) Exempt estates: the estate passes entirely to the spouse/civil partner (s18 IHTA, spousal exemption) or to charity (s23 IHTA), no IHT due regardless of value. For spouse estates: IHT217 is used to transfer the unused NRB to the surviving spouse's estate (instead of the full IHT402 process). (3) Foreign domicile / low-value UK estate: the deceased was non-UK domiciled; UK estate is below £150,000. For testate excepted estates: the PA1P probate application includes a declaration that the estate is excepted; no separate IHT205 form is needed since the 2022 reforms (the declaration is within the PA1P). Executors must be careful: if the deceased made large gifts in the 7yr before death (CLTs or PETs above exemptions), the estate may NOT qualify as excepted even if the residual estate is below the threshold. The cumulative gift history is included in the reporting scope.
Frequently Asked Questions
What is the IHT400 form and when do you need to complete it?
The IHT400 is HMRC's main inheritance tax account (return). You complete the IHT400 when the estate is not an 'excepted estate', i.e., when IHT is due, or when the estate exceeds the threshold, or when the deceased made significant gifts in the 7 years before death that need to be reported. The IHT400 must be submitted to HMRC BEFORE applying for a grant of probate, and the IHT must be paid (or a valid instalment election made for qualifying assets) before probate is granted. After HMRC processes the IHT400, it issues the IHT421, which is attached to the probate application (PA1P for testate estates; PA1A for intestate). If the estate is below £1 million and IHT is zero (an 'excepted estate'), a simplified declaration on the probate form (or IHT205 in older returns) can be used instead of the full IHT400.
What are the main supplementary schedules to the IHT400?
The IHT400 has over 17 supplementary schedules, each covering a specific type of asset or claim. The most important are: IHT402 (transferred NRB from deceased spouse, must be actively claimed; NOT automatic); IHT403 (gifts in 7yr before death; normal expenditure from income claims); IHT405 (houses and land, professional valuations); IHT411 (listed shares, ¼-up rule at date of death); IHT413 (business property relief, BPR; trading test; 2yr minimum holding; £1m cap from April 2026); IHT435 (RNRB claim, NOT automatic); IHT436 (transferred RNRB, NOT automatic); IHT430 (36% reduced rate for estates with 10%+ charitable legacies). Executors need to identify which supplementary schedules apply to the deceased's estate and complete each one accurately, HMRC will query incomplete or inconsistent schedules.
What is the IHT421 and why does probate depend on it?
The IHT421 is a form issued by HMRC after processing the IHT400. It confirms to the probate registry that the IHT position has been addressed, that IHT has been paid (or an instalment election made), and the estate's IHT account has been submitted. The executor CANNOT apply for a grant of probate without the IHT421. HMRC sends the IHT421 directly to the probate registry (or to the executor, who then includes it with the probate application, the process depends on whether the application is online or paper). The IHT421 effectively 'unlocks' the probate process. Processing time: HMRC typically takes 8-12 weeks to process the IHT400 and issue the IHT421. For complex estates with BPR, foreign assets, or disputed valuations, it can take longer. The grant of probate is usually issued 4-8 weeks after a complete probate application is submitted.
Can I claim the transferred NRB (tNRB) on the IHT400?
Yes, but you MUST claim it using IHT402. The transferred NRB (s8A IHTA 1984, allowing the estate to use any unused NRB percentage from a previously deceased spouse or civil partner) is NOT automatic. If you do not complete IHT402 and submit it with the IHT400, HMRC will NOT apply the tNRB. The evidence required for IHT402: death certificate of the first deceased spouse; grant of probate or letters of administration from the first estate; evidence of what NRB was used at the first death (IHT400 or estate accounts if available; or confirmation that no IHT was payable). If the first death documents are unavailable: contact HMRC IHT office (Nottingham), they retain historical records and may be able to confirm the NRB position at the first death. The tNRB is worth up to £325,000 additional NRB in 2026/27. For couples who pass everything to each other on the first death (using the full s18 spousal exemption), the full 100% tNRB is available at the second death. Similarly, IHT436 must be completed to claim the transferred RNRB, also not automatic.
What happens if you make a mistake on the IHT400?
If the IHT400 is submitted with incorrect information: (1) Underestimated asset values: if HMRC's District Valuer challenges a property valuation, or if assets are later found to be worth more, the executor submits a Corrective Account (C4 form) and pays the additional IHT plus HMRC interest from the original due date. (2) Overestimated values: the executor submits a Corrective Account and HMRC repays the overpaid IHT (with HMRC repayment interest). (3) Fraudulent or negligent inaccuracies: HMRC can impose penalties under Finance Act 2007, Sch 24, typically 0-30% of the understated IHT for 'careless' errors; 30-70% for 'deliberate' errors; 70-100% for 'deliberate and concealed' errors. HMRC can open an enquiry into an IHT400 at any time within 6 years of the filing date (or longer in cases of fraud). The best approach: take professional advice on valuations and BPR claims; ensure the IHT403 gifts schedule is comprehensive; claim all exemptions proactively (tNRB, tRNRB, RNRB) rather than letting them lapse.
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