How to Fill Out and Submit the IHT421: Inheritance Tax Probate Summary

The IHT421 form is the Inheritance Tax probate summary used in Northern Ireland. Executors and administrators send it to HMRC with the full Inheritance Tax account (Form IHT400) so HMRC can confirm the estate’s tax position and then notify the Probate Registry directly, clearing the way for a grant of representation.¹

The form applies only to Northern Ireland. Estates in England and Wales receive probate figures and a unique reference code from HMRC digitally instead, and Scottish estates use Form C1.

When You Need to File an IHT421

You need the IHT421 when the estate requires a full IHT400 account and the grant of representation is being applied for in Northern Ireland. Estates that qualify as “excepted estates” skip both the IHT400 and the IHT421.

An estate is excepted if any of the following applies:

The total value is under the £325,000 nil-rate band.
The estate is worth £650,000 or less and unused nil-rate band is being transferred from a spouse or civil partner who died first.
The estate is worth less than £3 million and everything passes to a surviving spouse, a UK-resident civil partner, or a qualifying charity.
The deceased was domiciled outside the UK and their UK assets are worth £150,000 or less.

Even a low-value estate has to file the full account (and therefore the IHT421) if it exceeds certain complexity thresholds: more than £3 million total value, foreign assets over £100,000, trust assets over £250,000, or lifetime gifts over £250,000 in the seven years before death.²

What to Have Ready Before You Start

The IHT421 is short. It is a summary that pulls figures straight from the IHT400 and its schedules, so you cannot fill it in until the full account is complete. Have the following in front of you:

The death certificate, so the deceased’s full legal name, date of death, and last address are recorded exactly as they appear there.
The completed IHT400. The IHT421 references box 79 (UK estate value), boxes 83 and 84 (liabilities), and box 119 (tax paid).
Schedule IHT404 if the estate includes jointly owned assets. The IHT421 pulls figures from IHT404 boxes 11, 12, and 13.³
Your Inheritance Tax reference number. Apply for this from HMRC at least three weeks before you intend to make any tax payment, online or by post using Form IHT422.⁴
The deceased’s domicile at the date of death, which the form asks for directly.

How to Complete the Form

Download the current version of the IHT421 from GOV.UK. HMRC recommends opening the PDF in Adobe Reader, completing it on screen, and printing it once you are done.¹ The form itself is quick, but errors here will hold up the probate application.

Deceased’s Details

Enter the title, surname, first names, date of death in DD MM YYYY format, last address with postcode, and domicile at the date of death. Copy the name exactly as it appears on the death certificate. Any mismatch with your probate application will be queried by the Probate Registry.

The Financial Summary Boxes

Six numbered boxes build the probate figures:

Box 1, estate in the UK before deductions: add IHT400 box 79 and IHT404 box 13. This is the total value of UK assets that became property of the personal representatives.
Box 2, joint assets passing by survivorship: copy from IHT404 box 11 (column A total). These pass automatically to a surviving joint owner and are excluded from the probate value.
Box 3, gross value of assets for probate: box 1 minus box 2. This is the headline figure the Probate Registry uses.
Box 4, liabilities: add IHT400 box 83, IHT400 box 84, and IHT404 box 12. Covers debts, mortgages, funeral expenses, and other allowable deductions.
Box 5, net value: box 3 minus box 4. Determines the probate court fees.
Box 6, tax and interest already paid: copy from IHT400 box 119, IHT400 Calculation box 65, or IHT430 box 28, whichever applies. Enter zero if no tax is due.³

What the Summary Deliberately Leaves Out

The IHT421 excludes several categories of assets that do appear on the IHT400: lifetime gifts made within seven years of death, foreign assets, assets held in trust, nominated assets, and gifts with reservation. These still feed into the overall Inheritance Tax calculation, but they are not part of the estate the Probate Registry grants authority over, so they do not belong in the probate summary totals.

How to Submit the Form

Print the completed IHT421 and post it to HMRC together with the IHT400, every supplementary schedule, and any IHT423 direct payment forms you are using to settle tax from the deceased’s bank accounts. The address is:

Inheritance Tax
HMRC
BX9 1HT
United Kingdom¹

Do not send the IHT421 to the Probate Registry yourself. HMRC reviews the figures and, once satisfied, forwards the cleared summary directly to the registry. Executors no longer receive a stamped copy back; HMRC sends the confirmation straight to HMCTS Probate.

How Long to Wait Before Applying for Probate

Allow around 21 days after HMRC receives your paperwork before you submit the probate application. That is how long it takes for HMRC to process the account and send clearance to the Probate Registry.⁵

This is where most avoidable delays happen. Applications that reach the Probate Registry before HMRC’s notification cannot be processed and sit in a queue. Count 21 days from the date HMRC received the papers, then apply. Once the registry confirms it has the cleared IHT421 on file, the grant of representation can be issued.

Correcting Figures After You Have Filed

Values sometimes shift after submission: a property sells for less than its probate valuation, an unknown account surfaces, a debt turns out larger than estimated. When that happens, file a corrective account using Form C4. HMRC uses the C4 to recalculate tax owed or refund any overpayment.⁶

Download the C4 from GOV.UK, complete it in Adobe Reader, then print and post it to HMRC. If the correction changes the gross or net estate value, the Probate Registry will also need to be told, and a significant change may require an amended grant.

Paying the Tax Alongside the Form

Inheritance Tax is due by the end of the sixth month after the person died. Interest accrues automatically from that point; the rate on late payments is 7.75 percent as of January 2026.⁷

Because estate money is usually locked in bank accounts until probate is granted, executors often use the Direct Payment Scheme: a separate Form IHT423 for each bank, building society, or National Savings account authorises that institution to transfer funds straight to HMRC. The scheme covers the tax and any accrued interest, but not court fees.⁸ Certain assets (property being retained, business assets, agricultural land, controlling shareholdings, and some unlisted shares) qualify for payment by ten equal annual instalments if you indicate the choice on the IHT400. Interest still applies to the outstanding balance.⁹

1
GOV.UK. Inheritance Tax Probate Summary for Northern Ireland (IHT421)
2
GOV.UK. How to Value an Estate for Inheritance Tax and Report Its Value
3
HM Revenue and Customs. IHT421 – Probate Summary Northern Ireland
4
GOV.UK. Pay Your Inheritance Tax Bill – Get a Payment Reference Number
5
HM Courts & Tribunals Service. Working Together to Avoid Delays to Probate Applications
6
GOV.UK. Inheritance Tax – Corrective Account
7
GOV.UK. Inheritance Tax Thresholds and Interest Rates
8
GOV.UK. Inheritance Tax Account (IHT400)
9
GOV.UK. Pay Your Inheritance Tax Bill – In Yearly Instalments