Which schedule you actually need — the 6 April 2025 fork
Before the first box, one question decides everything: did the person die before or after 6 April 2025?
On that date inheritance tax stopped asking where someone was domiciled and started asking whether they were a long-term UK resident. The form you need depends on the answer.
Deaths up to 5 April 2025 — IHT401
The connecting factor is domicile, including deemed domicile under the old rule (UK-resident for 15 of the previous 20 tax years).
If you have claimed the deceased was not domiciled in the UK, IHT401 is the schedule that supports the claim, and this walkthrough covers it box by box.
Nothing about a pre-6-April-2025 death is affected by the reform.
Deaths on or after 6 April 2025 — IHT401 only for treaty cases
The form's own instruction is narrow: fill it in for a death on or after 6 April 2025 only where a double taxation convention applies because of the deceased's domicile.
HMRC's IHT400 Notes put it the same way at box 6b.
That is the one surviving route into IHT401 after the reform — because four of the ten UK conventions pre-date 1975 and allocate taxing rights by domicile, so domicile can still decide the outcome even though domestic law no longer uses it.
Deaths on or after 6 April 2025 — IHT401a in every other case
If you are claiming the deceased was not a long-term UK resident, the schedule is IHT401a, covered in full at section 7 below.
You then complete the rest of the IHT400 with UK assets only — with one exception HMRC spells out: lifetime transfers made while the person was a long-term UK resident (or before 6 April 2025 while UK-domiciled) still belong on the account.
When neither schedule is needed
Where the deceased was not a long-term UK resident at death, had never been one since 6 April 2025, was never UK-domiciled or deemed domiciled before that date, and the UK estate consisted only of cash or listed shares and securities passing under a will, intestacy or by survivorship with a gross value of no more than £150,000, the estate is an excepted estate.
The return is then form IHT207 rather than an IHT400 — so there is no schedule to complete at all.
Why most guidance on this form is out of date
The reform is recent, and the great majority of IHT401 guidance in circulation was written when domicile was still the test.
It reads plausibly and it is wrong for any death from 6 April 2025.
Check the date on anything you rely on — including this page, which was checked against form IHT401 (HMRC 04/25), form IHT401a (HMRC 12/25) and the IHT400 Notes (04/26) in August 2026.
Before the first box, one question decides everything: did the person die before or after 6 April 2025?