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IHT402 is the supplementary schedule used to claim the transferable nil rate band (TNRB) — the portion of a deceased spouse or civil partner's inheritance tax allowance that was unused on their death and can now be applied to the second estate. Submitting IHT402 correctly can reduce or eliminate inheritance tax on the second death, potentially saving tens of thousands of pounds.
Every individual has a nil rate band (NRB) — the amount they can leave free of inheritance tax. In 2026/27, the NRB is £325,000. When a married person or civil partner dies and leaves assets to their surviving spouse, those assets are usually exempt from inheritance tax entirely. As a result, the first spouse may use little or none of their NRB.
IHT402 allows that unused NRB to be transferred to the surviving partner's estate when they die. The key principle is that the transfer is calculated as a percentage of the NRB, not a fixed cash amount. That percentage is then applied to the NRB in force at the date of the second death.
This means that even if the first spouse died many years ago when the NRB was lower, the transferred allowance is uplifted to today's value — a significant benefit for older estates.
Example: Margaret died in 2005 when the NRB was £275,000. She left her entire estate to her husband David, so her NRB was 100% unused. David dies in 2026 when the NRB is £325,000. His estate can claim 100% of £325,000 (his own NRB) plus 100% of £325,000 (the transferred NRB) = £650,000 combined NRB.
You need to complete IHT402 when all of the following apply:
If the deceased was widowed more than once, you may be able to transfer unused NRB from multiple previous spouses, up to a maximum of 100% of the NRB at the second death (so the combined NRB can never exceed twice the current NRB, regardless of how many previous spouses there were).
The calculation has two steps:
Patricia left her entire estate to her husband Robert. The NRB at her death was £325,000 and she used none of it (because the spouse exemption applied). Percentage unused: 100%. Robert dies when the NRB is still £325,000. Transferable NRB = 100% × £325,000 = £325,000. Robert's combined NRB = £650,000.
Jean died when the NRB was £325,000. She left £100,000 to her children (using £100,000 of her NRB) and the rest to her husband. Percentage used: £100,000 ÷ £325,000 = 30.8%. Percentage unused: 69.2%. Her husband dies when the NRB is £325,000. Transferable NRB = 69.2% × £325,000 = £224,900 (rounded to the nearest £1). His combined NRB = £325,000 + £224,900 = £549,900.
Charitable gifts are also exempt from inheritance tax. If the first spouse left their entire estate to charity (rather than to the surviving partner), 100% of their NRB remains unused — a full transfer is still available.
Important: The calculation uses the NRB at the second death, not the first. If the NRB increases between the two deaths, the transferred amount is automatically uplifted. If the government freezes the NRB (as it has done from 2021 to 2030), the transferred amount stays at the current frozen figure.
HMRC requires evidence about the first spouse's estate to verify the percentage of NRB that was unused. Gather the following before completing IHT402:
If the first spouse died many years ago and records are difficult to locate, HMRC will usually accept a statutory declaration from someone with knowledge of the estate, combined with whatever evidence is available. It is worth searching for old solicitors' files, which probate firms are required to retain for extended periods.
IHT402 has 12 main questions. Here is a plain-English guide to each:
IHT402 transfers only the standard nil rate band (NRB). If you also want to transfer unused Residence Nil Rate Band (RNRB) from the first spouse, you must complete IHT436 as a separate schedule alongside IHT435. These are entirely different forms for entirely different allowances, even though both relate to the spouse's unused tax-free bands.
IHT405 lists all property, land, and buildings in the estate for inheritance tax. Get the valuation right to avoid HMRC enquiries. Step-by-step completion guide.
IHT406 lists all bank accounts, savings, and ISAs in the estate. How to get date-of-death balances, handle joint accounts, and include accrued interest.
IHT407 covers furniture, jewellery, cars, art, and personal items in the estate. How to value household goods for HMRC, when professional valuations are needed.
IHT419 deducts debts from the taxable estate — mortgages, credit cards, loans, care fees. Which debts HMRC allows and common mistakes that trigger enquiries.
IHT435 claims the Residence Nil Rate Band (up to £175,000). Conditions, downsizing rules, taper for estates over £2m. Step-by-step guide.
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