IHT421 is HMRC's probate summary, and it's now only for estates applying for a grant of representation in Northern Ireland. You fill it in alongside the IHT400 and send both to HMRC, which uses it to confirm the figures the court needs for the grant. In England and Wales HMRC sends probate figures and a unique reference instead, and in Scotland you use form C1 for confirmation.
Everything below comes from GOV.UK's IHT421 page, the IHT421 form (HMRC 01/24), the GOV.UK guide to postponing Inheritance Tax and HMRC's Inheritance Tax Manual, as of October 2026.
Which form for which part of the UK
| Where the grant is applied for | What you send or get |
|---|---|
| Northern Ireland | IHT421 probate summary, with the IHT400 |
| England and Wales | No IHT421: HMRC sends probate figures and a unique reference |
| Scotland | Form C1, to apply for confirmation |
If you've seen IHT421 listed for an English or Welsh estate, check the date of that guidance: the current GOV.UK page limits the form to Northern Ireland, and its title says so.
What the IHT421 summarises
The form takes figures you've already worked out on the IHT400 and its schedules. It covers the property that passed to the executors or administrators for distribution, which is the same property you're applying for the grant on.
- Box 1: the estate in the UK before deductions (IHT400 box 79 plus IHT404 box 13).
- Box 2: joint assets that pass by survivorship (from the IHT404).
- Box 3: the gross value for probate, box 1 minus box 2.
- Box 4: liabilities (IHT400 boxes 83 and 84 plus IHT404 box 12).
- Box 5: the net value, box 3 minus box 4.
- Box 6: tax and interest paid on the account. If there's no tax to pay, you enter 0.
What it deliberately leaves out
The form says plainly that it's a summary for probate purposes only, so it won't match the total Inheritance Tax picture. It doesn't include:
- lifetime gifts
- foreign assets
- assets held in trust
- nominated assets
- gifts with reservation and pre-owned assets
This is the insight that saves a panic. A probate summary that's far lower than the IHT400 total isn't an error: joint property passing by survivorship and the items above sit outside the grant, even though some of them still count for tax.
Tax usually comes before the grant
GOV.UK says you must pay some or all of the Inheritance Tax before you can get a grant, and the tax is due by the end of the sixth month after the death. HMRC's due-date table runs month by month: a death in January means tax is due by 31 July, with interest from 1 August.
If you can't reach the estate's funds before the grant, you can ask HMRC to postpone some or all of the tax and interest until after it's issued, known as a grant on credit. In Northern Ireland that request goes in with the IHT400 and the IHT421, plus a signed letter headed 'Grants on credit' with your Inheritance Tax reference. The letter must confirm you can't release funds from the estate, state the most you can pay, and explain how you'll raise the rest. HMRC's manual says that once the letter, IHT421 or C1 is issued, the tax has to be paid promptly in line with that undertaking.
Ways to pay before the grant
Before asking for a grant on credit, GOV.UK expects you to try the routes that let the deceased's own assets pay the tax directly:
- bank, building society or NS&I accounts, through the Inheritance Tax Direct Payment Scheme
- British government stock
- cash funds inside a share or investment portfolio, if the stockbroker or fund manager will release them
- insurance and investment bonds, where the provider agrees to release funds to HMRC
If HMRC allows a grant on credit, it may place a notice of the Inheritance Tax charge against land or buildings in the estate at the Land Registry. That doesn't stop a sale, but it protects HMRC's interest.
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Filling it in and sending it
- Finish the IHT400 and every schedule first, including the IHT404 for joint assets, because the IHT421 boxes copy from them.
- Read the 'Applying for a grant' guidance notes in the IHT400 notes before you start, as the form tells you to.
- Give the deceased's details, the Inheritance Tax reference if you have one, and a contact name and phone number.
- Complete boxes 1 to 6 using the figures above.
- Print it and post it to Inheritance Tax, HMRC, BX9 1HT, United Kingdom, with the IHT400.
- Wait for HMRC to issue the IHT421 back to you before you apply for the grant in Northern Ireland; HMRC's manual describes the IHT421 being issued once the account is dealt with.
If the estate also earns income while you're dealing with it, the income tax side runs on its own calendar, so keep the UK tax year dates and the Self Assessment deadline in view.
The verdict
Only reach for the IHT421 if the grant is being applied for in Northern Ireland. In England and Wales, wait for HMRC's probate figures and unique reference; in Scotland, use the C1. Wherever you are, the real deadline is the tax one, six months after the death, so line up how the tax will be paid before you chase the grant.
Frequently asked questions
Is IHT421 still used in England and Wales?
No. GOV.UK now describes IHT421 as the probate summary for Northern Ireland. For estates in England and Wales, HMRC sends probate figures and a unique reference instead.
What do you use instead of IHT421 in Scotland?
Form C1, which is used to apply for a grant of confirmation.
Why is the IHT421 figure lower than the IHT400 total?
It's a probate summary only. It leaves out lifetime gifts, foreign assets, trust assets, nominated assets, gifts with reservation and joint assets passing by survivorship.
Where do I send form IHT421?
Print it and send it with the IHT400 to Inheritance Tax, HMRC, BX9 1HT, United Kingdom.
Can I get a grant before paying the Inheritance Tax?
You can ask HMRC for a grant on credit if you can't release funds from the estate. In Northern Ireland you include the IHT421 and a 'Grants on credit' letter with the IHT400.
When is Inheritance Tax due?
By the end of the sixth month after the death. For a death in January, the tax is due by 31 July, with interest charged from 1 August.
