HMRC IHT Reference Number UK (2026): How to Apply and What It's For

An HMRC IHT reference number (sometimes called the IHT reference or inheritance tax reference) is a unique reference issued by HMRC's Inheritance Tax team to identify an estate for inheritance tax purposes. You need an IHT reference number in the following circumstances: (1) When inheritance tax is due: if the estate exceeds the available nil-rate band (£325,000 in 2026/27 plus any transferable NRB from a late spouse, and the RNRB up to £175,000 where applicable) and there is IHT to pay, you must obtain an IHT reference before making any payment to HMRC. You cannot pay IHT without the reference — HMRC cannot allocate the payment to the correct estate without it; (2) When submitting an IHT400 form: if the estate requires the full IHT400 account (rather than the simpler excepted estate process), you must have the IHT reference before filing the IHT400 with HMRC. The IHT400 must be submitted before the Grant of Probate is issued; (3) All correspondence with HMRC IHT team: the reference must be quoted on all correspondence, enquiry forms, and payment documentation. Without it, HMRC cannot process correspondence; (4) When do you NOT need an IHT reference? If the estate is an 'excepted estate' (total value under the IHT threshold after reliefs, no chargeable transfers within 7 years, no complex structures), you submit a simplified return as part of the probate application and do not need to obtain a separate IHT reference from HMRC. In England and Wales, excepted estates use form IHT207 (overseas domicile) or the online probate service which incorporates the excepted estate declaration. If no IHT is payable and the estate is straightforward, no IHT reference is required. (5) IHT reference is NOT the same as the probate reference: the probate reference is issued by the HMCTS Probate Registry when a Grant of Probate or Letters of Administration is issued. These are two separate references from two separate government departments.

There are two ways to apply for an IHT reference number: (1) Online via form IHT422 (recommended — fastest): apply at tax.service.gov.uk/inheritance-tax/get-an-inheritance-tax-reference. You will need: (a) the deceased's full name; (b) the date of death; (c) the deceased's National Insurance number (if known); (d) the deceased's last known address; (e) your own details as the person applying (executor, administrator, or authorised agent/solicitor). The online application takes around 15–20 minutes. Processing time: HMRC typically generates the reference within 3–5 working days of the online application; however, HMRC does NOT send the reference back online or by email. The reference is always sent by post to the address provided; allow 15 working days from the date of application to receive it by post. If you have not received it after 15 working days, call HMRC IHT helpline on 0300 123 1072; (2) Paper form IHT422: if you prefer to apply by post, download form IHT422 from gov.uk, complete it, and post to HMRC Inheritance Tax, BX9 1HT (no street address needed — this is HMRC's BX9 mailbox for IHT correspondence). Processing time: significantly longer by post — allow 4–8 weeks; (3) Who can apply: the personal representative (executor named in the will, or administrator under a Grant of Letters of Administration) is the primary applicant. A solicitor or tax adviser acting for the estate can apply on the estate's behalf. Neither the beneficiaries nor a bank can apply; (4) Apply early: because the reference arrives by post (allow 15 working days from online application), submit the IHT422 application as soon as you know IHT will be due — ideally within the first 2–3 months of the estate administration, well before the 6-month payment deadline.

The inheritance tax payment deadline is 6 months from the end of the month in which the death occurred: (1) How the deadline is calculated: if the deceased died on any day in March 2026, the end of that month is 31 March 2026. Add 6 months: the IHT payment deadline is 30 September 2026. It makes no difference whether the deceased died on 1 March or 31 March — the deadline is the same for everyone who dies in the same calendar month; (2) Examples: (a) death on 15 January 2026 → deadline 31 July 2026; (b) death on 3 October 2025 → deadline 30 April 2026; (c) death on 29 February 2026 → deadline 31 August 2026; (3) Why this matters — interest: if IHT is not paid by the deadline, HMRC charges statutory interest on the unpaid amount from the deadline date. The HMRC interest rate for IHT underpayments in 2026 is linked to the Bank of England base rate. Interest runs daily from the deadline until payment. Penalties can also be charged for delayed submission of the IHT400 (not just late payment); (4) Payment before Grant: probate cannot be obtained until HMRC has confirmed that IHT has been paid (or that the estate is an excepted estate). In practice: IHT must be paid to HMRC using the IHT reference before the Probate Registry will issue the Grant. But the estate's assets are frozen until the Grant is issued. This creates the 'IHT funding problem': the estate's money cannot be accessed without a Grant, but IHT must be paid before a Grant can be obtained; (5) Solving the IHT funding problem: (a) direct payment scheme: banks and NS&I allow IHT to be paid direct from the deceased's accounts on sight of a completed form IHT423 (completed by the executor) + proof of death certificate (not a Grant). This is the most common solution. The account is not 'fully available' but the bank pays HMRC directly; (b) other sources: executor's own funds (reimbursable from the estate after Grant); life insurance payout in trust (not part of estate so immediately available); other joint assets that passed outside the estate; short-term executor loan; (6) IHT on property — instalment option: inheritance tax on land, buildings, unlisted shares and certain business assets can be paid in 10 equal annual instalments (IHTA 1984 s.227) rather than as a lump sum by the 6-month deadline. Interest is charged on outstanding instalments. Election for instalment option should be made on the IHT400 before or at the deadline.

The IHT400, IHT reference, IHT421, and probate application form a sequential process — each step depends on the previous one: (1) Step 1 — Obtain IHT reference (IHT422): apply online as described above. Receive reference by post; (2) Step 2 — Complete IHT400: complete the full IHT account (IHT400 + relevant schedules). Quote the IHT reference in the IHT400. Submit to HMRC; (3) Step 3 — Pay IHT (using IHT reference): use the IHT reference to make payment to HMRC before the 6-month deadline. Payment can be by direct payment from the deceased's bank account (form IHT423), cheque to HMRC, or bank transfer (quoting the IHT reference). Instalment option: if elected, pay the first instalment only by the deadline; (4) Step 4 — HMRC issues IHT421: after receiving and processing the IHT400 and confirming that at least the non-instalment IHT has been paid, HMRC sends form IHT421 directly to the Probate Registry (from April 2021, HMRC sends IHT421 electronically to HMCTS — executors no longer receive a paper IHT421 to include with their probate application; instead, HMRC notifies the Probate Registry directly); (5) Step 5 — Apply for Grant of Probate: the personal representative submits the probate application (PA1P + original will + payment of £300 probate fee). The Probate Registry checks that HMRC has confirmed the IHT position (by electronic IHT421 from HMRC). The Registry will not issue the Grant until the IHT421 is received from HMRC; (6) Step 6 — Grant issued: the Probate Registry issues the sealed Grant of Probate (or Letters of Administration); (7) Key point: if there is no IHT due (excepted estate), the IHT421 process is simplified. For excepted estates using the online probate service, HMRC confirmation is built into the process and there is no separate IHT422/IHT400 requirement.

Practical IHT reference checklist for executors: (1) Do you need a reference at all? Check whether the estate is likely to be an excepted estate (total estate value under the threshold after reliefs; no IHT due; straightforward assets). If yes, you may not need a reference — the online probate service handles this. If IHT is likely to be due, apply for the reference immediately; (2) Apply online as early as possible: the reference arrives by post — allow 15 working days. If you apply on day 30 after death and it takes 15 working days, you still have time before the 6-month deadline. But delays in administration mean you could be cutting it fine — apply early; (3) Keep a note of the reference: the HMRC IHT reference is typically in the format 'IHT reference: [number]'. Keep the HMRC letter in the estate file; (4) Use the reference on all correspondence: on the IHT400, on IHT423 bank direct payment forms, in any letters to HMRC, and on any cheques; (5) Check your bank's direct payment scheme: the IHT direct payment scheme (form IHT423) is the standard way to pay IHT from the deceased's bank or building society accounts without a Grant. The bank pays HMRC directly from the account. Not all accounts qualify — National Savings & Investment accounts, most bank current/savings accounts, and NS&I Premium Bonds qualify. Stocks and shares ISAs and investment accounts do NOT qualify for direct payment; (6) Track HMRC's response: after submitting the IHT400, HMRC may raise enquiries (HMRC Compliance Checks are common for larger estates). Respond promptly — delays in satisfying HMRC's queries delay the IHT421 and therefore the Grant; (7) For instalment option elections: if you elect to pay IHT on property in instalments (IHTA 1984 s.227), you only need to pay the first instalment before probate — but you must still have the IHT reference and have submitted the IHT400.