Form IHT402: claiming a transfer of unused nil rate band

What is form IHT402?

Form IHT402 is called "Inheritance Tax: claim to transfer unused nil rate band" on GOV.UK, one of the supplementary schedules to form IHT400, the full Inheritance Tax account.

Form IHT402 transfers any unused Inheritance Tax threshold from a spouse or civil partner who died first to the estate you are dealing with now (GOV.UK). As of August 2026, the nil rate band is £325,000, applying from 6 April 2009 to 5 April 2031, and anything above it is taxed at 40%.

Where the first person left everything to their spouse or civil partner, none of their threshold was needed, so the survivor's estate can claim a second £325,000 and reach £650,000. See the inheritance tax threshold for background.

Who needs to complete form IHT402?

Three things have to be true: you are sending form IHT400, the person who died had a spouse or civil partner who died before them, and some or all of that person's nil rate band went unused.

The claim is made by the personal representatives, usually the executor or administrator. If you are not at that stage, how to apply for probate sets out the sequence.

What information does form IHT402 ask for?

Form IHT402 is about the first death, not the second. It asks who the spouse or civil partner was and how much of their nil rate band was left unused.

So you need to know what that first estate was worth and who inherited it. Anything left to the surviving spouse or civil partner, or to a qualifying charity, does not use up the threshold.

Where none of the first threshold was used, the transfer is the full 100%, reaching £650,000. Where only part was unused, form IHT402 works it out as a percentage: the unused band from the first death, divided by the band that applied then, multiplied by 100, applied to the band in force at the second death (GOV.UK). GOV.UK's own example: 66.6666% of a £300,000 band gives £200,000.

GOV.UK asks for photocopies of three documents: the grant of representation for the first spouse or civil partner's estate (or their death certificate if none was taken out), their will if they left one, and any deed of variation that changed who inherited from that earlier estate.

Form IHT402 is interactive and needs Adobe Reader, the same as form IHT400, and you cannot save a partly completed copy, so gather everything first (GOV.UK).

How does form IHT402 fit with form IHT400?

Form IHT402 travels with form IHT400, but carries its own deadline too: 24 months after the end of the month of the second death, against IHT400's 12 months from the death itself (GOV.UK). After you send the Inheritance Tax forms, HMRC sends a unique code you need before applying for probate.

Form IHT402 is not the only transfer claim. Unused residence nil rate band, worth £175,000 as of August 2026, is claimed on form IHT436. Our guide to the residence nil rate band explains it in full.

What does the £650,000 figure mean for excepted estates?

An estate is usually excepted if it is worth £650,000 or less and any unused threshold is being transferred from a spouse or civil partner who died first (GOV.UK). Then you send neither form IHT400 nor form IHT402, and the values go on the probate application instead.

Full details are still needed with no tax to pay if the person gave away more than £250,000 in the 7 years before death, left more than £3 million, or held foreign assets over £100,000 (GOV.UK). For which schedules your estate needs, start with inheritance tax forms.

Frequently asked questions

Where do you download form IHT402?

Form IHT402 is published on GOV.UK at the page "Inheritance Tax: claim to transfer unused nil rate band (IHT402)". The address is https://www.gov.uk/government/publications/inheritance-tax-claim-to-transfer-unused-nil-rate-band-iht402. GOV.UK last updated that page on 6 April 2025, when it was revised for the 2025 to 2026 tax year.

Is the transferable nil rate band applied automatically?

No. HMRC only adds the unused threshold from the first spouse or civil partner if the personal representatives complete form IHT402 and send it with form IHT400. If nobody claims it, the estate keeps only its own £325,000 nil rate band.

What is the difference between form IHT402 and form IHT436?

Form IHT402 transfers unused nil rate band, £325,000 as of August 2026. Form IHT436 claims transferable residence nil rate band, a separate £175,000 allowance, and using it also requires claiming the residence nil rate band on the current estate with form IHT435.

Can unmarried partners transfer an unused nil rate band?

No. GOV.UK describes the transfer as coming from a spouse or civil partner who died first. A couple who lived together without marrying or forming a civil partnership create no transferable threshold, so the survivor's estate cannot reach £650,000 this way.

When does form IHT402 need to reach HMRC?

Two deadlines apply. Form IHT400 must be sent within 12 months of the death, and before you apply for probate. Form IHT402 itself must reach HMRC within 24 months of the end of the month of the second death (GOV.UK). Inheritance Tax must be paid by the end of the sixth month after the death.

Sorting out the accounts behind the figures

Claiming a transfer means proving what both estates held, usually by contacting bank after bank. Legacy Trail finds the accounts and services the person held and notifies them centrally.