IHT421 Form UK: The Probate Summary and How HMRC Notifies HMCTS
Updated: 13 June 2026 • Reading time: 7 min • By WillSafe UK Editorial Team
The IHT421is the document that bridges the inheritance tax process and the probate process. Before HMCTS will issue a grant of probate, it needs confirmation from HMRC that the estate’s inheritance tax position is settled. That confirmation comes via the IHT421 — officially the “Inheritance Tax: probate summary”. Critically, executors do not complete the IHT421 themselves: HMRC generates it after processing the IHT400 account, and since 2021 sends it electronically to HMCTS for online probate applications. This guide explains exactly how the IHT421 works, what executors need to do, and how to avoid common delays.
What Is the IHT421?
The IHT421 is HMRC’s formal acknowledgment to HMCTS that it has:
- Received and reviewed the IHT400 inheritance tax account for the estate
- Established the inheritance tax liability
- Confirmed that IHT has been paid, or that satisfactory arrangements are in place (for example, an instalment election for land or a business)
Think of it as a “tax clearance” for the purposes of probate — not a full certificate of discharge (that is the IHT30 certificate), but confirmation enough for HMCTS to issue the grant of representation. Without the IHT421 confirmation (or its equivalent for excepted estates), probate cannot proceed.
The 2021 Change: Electronic Notification to HMCTS
Before 2021, executors had to wait for HMRC to post them the physical IHT421, then include it with the paper probate application at the Probate Registry. This created significant delays: HMRC post to executor, executor post to Registry, Registry processing — a chain that added weeks to the probate process.
From 2021, for estates applying for probate online through the MyHMCTS portal, HMRC now sends the IHT421 directly and electronically to HMCTS. The process now works as follows:
- Executor submits IHT400 (and pays IHT) to HMRC Nottingham.
- HMRC processes the account and generates the IHT421.
- HMRC sends the IHT421 electronically to HMCTS and writes to the executor with the IHT421 reference number.
- Executor enters the IHT421 reference number in the online probate application on MyHMCTS.
- HMCTS verifies against the IHT421 it has received from HMRC and proceeds to issue the grant.
For paper probate applications still submitted by post to a Probate Registry, HMRC continues to send the IHT421 directly to the executor, who must include it with the paper application. The physical form is still used in this context.
What Executors Need to Do
The practical steps for online probate applications are straightforward:
- Submit the IHT400 to HMRC.Send the completed IHT400 and all applicable supplementary schedules (IHT405, IHT406 etc.) to HMRC’s Inheritance Tax office at BX9 1HT. Do this as early as possible — ideally 6–8 weeks before the 6-month IHT payment deadline to allow processing time.
- Pay the IHT by the 6-month deadline. Interest runs from the end of the sixth month after the month of death. Pay using the Direct Payment Scheme (IHT423) or by bank transfer. Do not wait for HMRC to acknowledge receipt before paying.
- Wait for HMRC’s IHT421 reference letter.HMRC will write to you once the IHT421 has been generated and sent to HMCTS. Keep this letter — it contains the reference number you need for the probate application.
- Submit the online probate application. On MyHMCTS, you will be prompted to enter the IHT421 reference number at the relevant question. Once entered, HMCTS links your probate application to the IHT421 already in its system.
- Wait for the grant. HMCTS will issue the grant of probate (or letters of administration) once it has matched the probate application to the IHT421 and processed the application fee.
How Long Does HMRC Take?
HMRC’s published target for processing IHT400s is 12 weeks from receipt of a complete account. In practice in 2025–2026:
- Straightforward accounts(standard estate, no BPR/APR, no complex lifetime gifts): typically 3–6 weeks.
- Complex accounts(business property relief, agricultural property relief, foreign assets, trusts, large lifetime gifts): 6–12 weeks or longer if HMRC raises queries.
- Formal HMRC enquiries: Can extend to many months if HMRC disputes valuations or relief claims.
If HMRC has not issued the IHT421 reference within 12 weeks of submitting a complete account, contact HMRC’s Inheritance Tax helpline (0300 123 1072). Have the estate reference, the date of submission, and the amount of IHT paid to hand.
IHT421 and Excepted Estates: No IHT421 Needed
Many estates — particularly since the 1 January 2022 changes to the excepted estate rules — do not need to file an IHT400 at all. For these estates, there is no IHT421 process. Instead, personal representatives provide estate summary information directly within the online probate application, without any HMRC involvement. If you are unsure whether your estate needs an IHT400 (and therefore an IHT421), check:
- Is IHT payable? If yes, IHT400 and IHT421 are required.
- Does the estate gross value exceed £3m? If yes, IHT400 required even if no IHT is payable.
- Was the deceased non-UK domiciled? Specialist advice needed — likely IHT400 required.
- Were there substantial lifetime gifts or gifts with reservation of benefit? IHT400 likely required.
- Does the estate include a trust in which the deceased had a beneficial interest? IHT400 required.
Common Problems and How to Avoid Them
1. Paying IHT but forgetting to submit the IHT400
Payment alone does not trigger HMRC to generate the IHT421. The IHT400 account must be submitted separately. HMRC matches the payment to the account but will not produce the IHT421 until the account has been submitted and reviewed.
2. Applying for probate before the IHT421 reference arrives
If you start the online probate application before receiving the IHT421 reference from HMRC, you can save the application as a draft. However, you cannot submit it until the reference is available. Do not attempt to proceed without the reference — HMCTS will reject the application.
3. Incomplete IHT400 schedules
Missing or incomplete supplementary schedules (e.g. no IHT405 for the family home, or no IHT403 for lifetime gifts) will cause HMRC to contact you for further information, pausing the IHT421 clock. Use HMRC’s IHT400 Notes booklet to work through which schedules apply.
4. IHT paid to wrong reference
IHT must be paid using the estate’s unique IHT reference number (starting with a letter, followed by digits — provided in HMRC’s initial acknowledgment of the IHT400). Payments without a correct reference are not matched to the estate and will delay the IHT421.
IHT421 vs IHT30 Certificate of Discharge
The IHT421 and the IHT30 Certificate of Discharge are often confused but serve entirely different purposes:
| Document | Purpose | When issued | Who receives it |
|---|---|---|---|
| IHT421 | Confirms IHT position to HMCTS so probate can proceed | After IHT400 processed and IHT paid | HMCTS (electronically) + executor (reference only) |
| IHT30 | Formally discharges executor from personal IHT liability | After estate fully administered and all IHT paid | Executor (on application) |
The IHT421 comes first — it is needed to get probate. The IHT30 comes last — it protects the executor after they have distributed the estate. Most executors apply for the IHT30 only on larger or complex estates where HMRC scrutiny is a realistic risk.
Frequently Asked Questions
What is the IHT421 form?
The IHT421 — officially titled ‘Inheritance Tax: probate summary’ — is the document HMRC issues after processing an IHT400 inheritance tax account. It confirms to HMCTS (His Majesty’s Courts and Tribunals Service) that the inheritance tax position has been established: either that IHT has been paid, that satisfactory arrangements have been made to pay it (for example via instalments), or that no IHT is due. HMCTS requires this confirmation before it will issue a grant of probate or letters of administration. The personal representative does not complete the IHT421 — HMRC produces it and sends it to HMCTS.
Do executors still need to send the IHT421 to the Probate Registry?
No — not for online probate applications. Since 2021, when an executor submits the IHT400 online or by post and the estate is applying for probate online via HMCTS, HMRC sends the IHT421 electronically and directly to HMCTS. The executor simply enters the IHT421 reference number (provided by HMRC) into the online probate application at MyHMCTS. There is no need to print, post, or physically attach the IHT421. For paper probate applications submitted by post to a Probate Registry, HMRC still sends the IHT421 to the applicant by post who must then include it with the paper probate application.
How long does HMRC take to issue the IHT421?
Once HMRC receives the complete IHT400 account and any accompanying schedules, and is satisfied that IHT has been paid (or appropriate arrangements are in place), it typically issues the IHT421 within 20 working days for straightforward accounts. In 2025–2026, HMRC has been running at 6–10 weeks for more complex accounts. HMRC’s published target is to process IHT400s within 12 weeks. Executors should submit the IHT400 and pay the IHT as early as possible — the IHT421 will follow. Do not wait for the IHT421 before paying IHT, as interest runs from the 6-month deadline regardless of whether HMRC has processed the account.
What is the IHT421 reference number and where do I find it?
When HMRC processes your IHT400, it assigns a unique reference number to your estate’s IHT421. For online probate applications, HMRC writes to the executor to confirm the IHT421 has been sent to HMCTS and provides the reference number. You enter this reference when completing the online MyHMCTS probate application at question ‘IHT reference’. The reference is typically in the format of your IHT reference number (starting with a letter followed by digits). Keep a note of all correspondence from HMRC’s Inheritance Tax office in Nottingham — the reference will be in their acknowledgment letter.
Can probate be applied for before HMRC issues the IHT421?
No. HMCTS will not issue a grant of probate until HMRC has confirmed the IHT position via the IHT421. This is why there is often a delay between paying the IHT and being able to proceed with probate administration — executors must wait for HMRC to process the IHT400 and issue the IHT421 (whether electronically or by post). The practical implication is that you should submit your IHT400 as early as possible, and certainly well before the 6-month IHT payment deadline, to avoid both interest on late payment and delays to probate. If HMRC is taking longer than 12 weeks, you can chase them via the HMRC IHT helpline.
Is an IHT421 required for excepted estates?
No. Excepted estates — those that do not need to file an IHT400 because they fall within the simplified excepted estate rules (broadly, estates below the IHT threshold, with gross value under £3m, no trusts, no substantial lifetime gifts, and UK domicile) — do not produce an IHT421 at all. Instead, for these estates the personal representative provides estate summary information directly within the online probate application. HMRC is not involved in the probate process for excepted estates: there is no IHT400, no IHT421, and no HMRC sign-off required. The change to excepted estate rules from 1 January 2022 significantly reduced the number of estates needing an IHT400 and IHT421.
Related IHT forms
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