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How to transfer unused residence nil rate band using IHT436

The residence nil rate band can effectively double for a widow or widower: whatever percentage of the allowance the first spouse didn't use transfers to the second estate.

For most bereaved couples where the first death was before 6 April 2017, that means a straightforward 100% uplift — the allowance didn't exist yet, so none of it was used.

But the claim has a firm 2-year deadline from the second death, a taper that reaches back to the size of the first estate even for deaths before the allowance existed, and an evidence requirement that can mean reconstructing an estate administered decades ago.

This walkthrough covers who can claim, the branching that decides which questions apply, the taper trap, and what evidence a decades-old first death actually requires.

✓ Official source checked 23 August 2026 · GOV.UK last revised this form 30 August 2022IHT436 on GOV.UK
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United KingdomInformational, not legal or financial adviceOfficial source: GOV.UK
Official form · always current

This is the same official IHT436 file HM Revenue & Customs publishes on GOV.UK — the link below fetches the current version live from GOV.UK the moment you click it, so it can never go out of date.

Current version: August 2022 · confirmed on GOV.UK 23 August 2026

This walkthrough takes IHT436 field by field, in plain English. Most of the form is administrative; the hard part is knowing the first estate's size still tapers the claim — even for a death decades before the residence allowance existed.

The thing most people get wrong
Assuming a pre-April-2017 first death automatically means the full 100% uplift.

The entitlement usually is 100% — because the RNRB didn't exist to be used — but the brought-forward allowance is still tapered against the FIRST spouse's estate: if that estate exceeded £2 million, the transferable amount shrinks by £1 for every £2 over, and a large-enough first estate extinguishes it entirely.

A 1990s first death with a substantial estate needs its value evidenced, not waved through — and executors who certify 100% without checking are signing a declaration HMRC can test.
The form, in summary
Valoren
IHT4363 pages27 fields guided
With Valoren30 minutes
Without Valoren1–3 hours
fast if the first estate's papers exist; slow archaeology if a decades-old first death has to be reconstructed
Deadline
2 yearsfrom end of month
of the second death
Who Files
Executorof the second estate,
with IHT435
£
Fee
Freeschedule to
IHT400
Filed with HMRC
Draws from your Estate File
the records this form is built from
PersonalCivil Dossier·Personal Record·Property Folio·Digital Access Map·Financial Accounts·Asset Inventory·Income & Outgoings·Policy Index·Legal Instruments·Medical Abstract·Succession Plan·Digital Legacy Registry·Business Interests & Directorships·Funeral & Committal Wishes·Dependent Care & Handoff·RegistryMaster Registry·Renewal Register·People, Authority & Contacts·Designated Places·Kinship & Succession Map·SecureAccess Controls·Recovery Routes·Custody & Contingency·EventsDeath & Estate Activation·Incapacity & Medical Proxy·Absence & Continuity Cover·Access Loss & Identity Recovery·Legal Dispute & Evidence Protocol·Theft & Asset Compromise·Property Damage & Incident Response·Relocation & Address Update Protocol·Separation & Custody Documentation·Business Interruption & Continuity·PersonalCivil Dossier·Personal Record·Property Folio·Digital Access Map·Financial Accounts·Asset Inventory·Income & Outgoings·Policy Index·Legal Instruments·Medical Abstract·Succession Plan·Digital Legacy Registry·Business Interests & Directorships·Funeral & Committal Wishes·Dependent Care & Handoff·RegistryMaster Registry·Renewal Register·People, Authority & Contacts·Designated Places·Kinship & Succession Map·SecureAccess Controls·Recovery Routes·Custody & Contingency·EventsDeath & Estate Activation·Incapacity & Medical Proxy·Absence & Continuity Cover·Access Loss & Identity Recovery·Legal Dispute & Evidence Protocol·Theft & Asset Compromise·Property Damage & Incident Response·Relocation & Address Update Protocol·Separation & Custody Documentation·Business Interruption & Continuity·
Legal basisStatute

Where the deceased had a spouse or civil partner who died first, any residence nil rate band unused at that first death can be transferred — 'brought forward' — and added to the survivor's own RNRB.

The transfer is expressed as a percentage of the first death's unused allowance, applied to the RNRB in force at the second death.

Two facts surprise almost everyone. First: if the first spouse died before 6 April 2017, the RNRB did not exist, so none of it was used — the survivor's estate can normally claim a full 100% uplift, no property at the first death required.

Second: the brought-forward allowance is still tapered by reference to the FIRST spouse's estate — if that estate exceeded £2 million, the transferable amount reduces by £1 for every £2 over, even for pre-2017 deaths when the allowance didn't exist.

IHT436 is the claim form; it branches sharply on whether any RNRB was actually used at the first death.

Section by section

The form, section by section.

Before you start, you’ll need:
  • Who Files — The executor or administrator of the second estate, alongside the IHT435 RNRB claim
  • 3 pages · 27 fields guided
  • Draws from your Estate File — Civil Dossier, Personal Record, Property Folio
Section 1

What the brought-forward allowance is

A percentage transfer, not a fixed sum — the same architecture as the transferable ordinary nil-rate band, applied to the residence allowance.

Percentage, applied at second-death rates

The unused proportion of the first death's RNRB transfers as a percentage and is applied to the allowance in force at the second death.

A 100% transfer at current rates means up to an extra £175,000 — on top of the survivor's own RNRB, their own nil-rate band, and any transferred ordinary nil-rate band from IHT402.

Only one prior death at a time — but serial marriages count

Where the deceased survived more than one spouse, brought-forward allowance can be accumulated from each, but the total uplift is capped at 100% of one full additional allowance.

The form asks about the marriage history — the Personal Record's previous-marriages section is exactly the source for it.

It needs the paired IHT435

IHT436 only transfers the allowance; the RNRB itself is claimed on IHT435 and still requires this estate to pass a qualifying residence to direct descendants (or qualify via downsizing).

No qualifying inheritance at the second death means nothing for the transferred allowance to attach to.

A percentage transfer, not a fixed sum — the same architecture as the transferable ordinary nil-rate band, applied to the residence allowance.

HM Revenue & Customs (HMRC) · IHT436
Section 2

The branch — was any RNRB used at the first death?

The form splits into two mutually exclusive paths at this question, and you complete only one.

No — including every death before 6 April 2017

If the first death was before 6 April 2017, the answer is automatically no: the allowance did not exist.

The simpler path applies — establish the marriage, the first death, and the first estate's value (for the taper), and the transfer is normally the full 100%.

Yes — first death on or after 6 April 2017 with a home passing to descendants

The longer path: compute the RNRB available at the first death (including any downsizing addition), how much was used against the home that passed to direct descendants, and therefore what percentage remains.

The first estate's IHT435, grant and estate accounts are the source documents.

Don't complete both

The two question sets are alternatives, and completing both is one of the most common reasons HMRC correspondence bounces the schedule back.

Route once at the branch question, then stay on that path.

The form splits into two mutually exclusive paths at this question, and you complete only one.

HM Revenue & Customs (HMRC) · IHT436
Section 3

The taper trap — the first estate's size still matters

The single most counterintuitive rule in the RNRB system, and the one that catches professionally-advised estates as well as lay executors.

£2 million measured at the FIRST death

If the first spouse's estate exceeded £2 million, the brought-forward allowance is reduced by £1 for every £2 of excess — even where the first death was before 6 April 2017 and the allowance could never have been used.

A first estate large enough tapers the transfer to nil.

The £2 million threshold is tested against the first estate's value before reliefs like business or agricultural relief are applied, which is precisely how large farming and business estates get caught.

Evidence of the first estate's value

For post-2017 first deaths the IHT papers usually exist.

For older deaths, the grant (which states a sworn estate value), estate accounts, or solicitors' files are the evidence.

Where the first estate was plainly modest, the declaration is straightforward — the care is needed exactly where the first estate was substantial.

The second estate's own taper is separate

Independently, the second estate's RNRB (including the transferred amount) tapers if the second estate exceeds £2 million.

The two tapers are computed separately and can both apply.

An estate near either threshold should model the numbers before assuming the headline allowances.

The single most counterintuitive rule in the RNRB system, and the one that catches professionally-advised estates as well as lay executors.

HM Revenue & Customs (HMRC) · IHT436
Section 4

Deadline and mechanics

A firm window, a paired form, and a small stack of certificates.

Two years from the end of the month of death

The claim must reach HMRC within 2 years of the end of the month in which the second death occurred.

HMRC has discretion to accept late claims in limited circumstances, but planning on that discretion is how allowances worth six figures get lost.

Diarise it from day one alongside the IHT402 window.

File with the IHT400 and IHT435

In practice all three travel together: the account, the RNRB claim, and this transfer claim.

Keep the property, descendant, and value figures consistent across the three — internal contradictions are the fastest route to a compliance check.

The certificate stack

Marriage or civil partnership certificate; the first spouse's death certificate; the first grant if one issued; and the first estate's value evidence.

Order missing certificates from the General Register Office early — they are cheap and quick, and the claim cannot be certified without the facts they establish.

A firm window, a paired form, and a small stack of certificates.

HM Revenue & Customs (HMRC) · IHT436

Many people file IHT436 themselves — that is what this walkthrough is for. If the estate behind it has stopped being simple — inheritance tax to pay, a trust, foreign assets, a dispute — Signum, Valoren’s own specialist desk, can take it on, and we say so plainly: it starts with a free intake, and if you do not need us, we will tell you. Prefer an independent adviser? STEP and the Chartered Institute of Taxation both keep public member directories, and neither pays Valoren a referral fee.

FAQ

IHT436 questions, answered.

The opposite: there is usually everything to transfer.

The RNRB only came into force on 6 April 2017; a spouse who died before then used none of it, so 100% of the brought-forward allowance is normally available to the survivor's estate — worth up to an additional £175,000 of tax-free allowance at current rates.

The one check that still matters is the size of the 1998 estate: over £2 million and the taper bites (see the pitfall).

You do not need the first spouse to have owned a home.
Then the form's second branch applies: you work out what percentage of their available RNRB was used when their estate passed a home to direct descendants, and the unused percentage transfers.

The two branches are mutually exclusive — the form routes you at the 'was any RNRB used?' question, and you complete one set of boxes, not both.
The marriage/civil partnership certificate, the first spouse's death certificate, a copy of the grant of probate if there was one, and evidence of the first estate's value and what passed to whom (the will, estate accounts, or the IHT papers if any were filed).

For old, small first estates where no IHT400 was ever filed, HMRC accepts the claim with the best available evidence — but the executor is declaring the facts, so gather what exists rather than asserting from memory.
Yes — they are separate transfers on separate forms: IHT402 for the ordinary nil-rate band, IHT436 for the residence allowance, both filed with the same IHT400 and both subject to the same style of two-year claim window.

A widowed person's estate passing a family home to children can, at current rates, shelter up to £1 million across the four allowances — but only if both claims are actually made, with evidence, in time.

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Where this fits

IHT436 is one form. The file behind it is the rest.

This claim runs on the paper trail of a marriage and an earlier death: certificates, the first grant, the first estate's value.

The Civil Dossier holds the certificates; the Personal Record's previous-marriages section (with its NRB-transfer flag) is where the first death's details live; the Property Folio carries the home the paired IHT435 claim turns on.

When you're ready — not before — our £179 Executor's First Hour walks you through registering the death, notifying banks and pensions, and getting probate started, in the right order. The free checklist above covers the essentials; this is for when you'd rather have a hand to hold. Executor's First Hour — £179

HM Revenue & Customs (HMRC)27 fieldsNo separate fee — supplementary schedule filed with IHT40030 minutes with Valoren
The return this attaches to

This is one schedule. It attaches to the IHT400 — the main Inheritance Tax account — which is where every schedule you complete comes together.

Next: IHT400
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