IHT402: transferring a late spouse’s unused nil rate band

Who needs IHT402

The schedule applies where (IHT402, page 1):

• the person whose estate you are dealing with died on or after 9 October 2007;
• their spouse or civil partner died before them;
• the first estate did not use all of its nil rate band, usually because most of it passed to the surviving spouse or it was smaller than the nil rate band.

For married couples the first death can be at any date. For civil partners it must be on or after 5 December 2005 (IHTM43001). Nothing transfers where the marriage or civil partnership ended in divorce or dissolution (IHTM43005).

The transfer is not automatic, and it is claimed only when the second spouse or civil partner dies. The personal representatives (the executors or administrators) make the claim (IHTA 1984 s.8B; IHTM43006) by answering Yes at IHT400 box 29c and sending IHT402 with the account. Where the death was on or after 1 January 2022 and the estate is an excepted estate (broadly, up to £650,000 with a transfer, if the other conditions are met; IHTM43064), the transfer is claimed on the probate application instead.

What uses up the nil rate band at the first death

The question is how much of the first spouse's nil rate band was used, not what the survivor inherited (IHTM43002, IHTM43020).

• Uses it up: chargeable legacies to anyone other than the surviving spouse (children or friends, for example), the first spouse's share of joint assets that passed to someone else, trust assets they could benefit from, gifts with reservation (gifts they kept benefiting from), and chargeable gifts in the 7 years before their death.
• Does not use it up: what passed to the surviving spouse, gifts to charity, and assets that qualified for 100% business or agricultural relief.

So if the first estate was smaller than the nil rate band, the balance is unused even if everything went to the children. For example, an estate of £150,000 left entirely to a son, when the nil rate band was £300,000, leaves 50% to transfer (IHTM43002).

What to gather about the first death

HMRC asks for photocopies of (IHT402, page 1; IHTM43006):

• the grant of representation (probate or letters of administration) for the first estate or, if there was no grant, the death certificate;
• the will, if there was one;
• any deed of variation or similar document that changed who inherited.

You will also need to know who inherited what, whether any assets were jointly owned or held in trust, and whether the first spouse made gifts in the 7 years before their death that became chargeable. The executor or solicitor who dealt with the first estate, or family members, may be able to help. Copies of grants and wills can be found through the probate records search on GOV.UK, and certificates through the General Register Office. The form asks you to make full enquiries so that the figures are correct.

Two notes on the form are worth knowing early. If the grant shows that tax or duty was paid on the first death, there is usually nothing left to transfer (note 1; IHTM43002 mentions one rare exception). If you are not sure whether an exemption or relief applied at the first death, say so, and HMRC will discuss it with you (note 5).

Boxes 9 to 21, step by step

1. Box 9: the nil rate band at the date of the first death (£325,000 for deaths from 6 April 2009; earlier figures are in HMRC's thresholds table).
2. Box 10: the chargeable value of gifts the first spouse made in the 7 years before their death, after exemptions.
3. Box 11: box 9 minus box 10.
4. Box 12: any residence nil rate band used on the first death (deaths on or after 6 April 2017 only). If you fill this in, include the home passing to direct descendants in box 13.
5. Box 13: legacies and assets passing under the will (or, without a will, the intestacy rules) to anyone other than the surviving spouse, at their chargeable value after exemptions and reliefs.
6. Box 14: the first spouse's share of jointly owned assets that passed to someone other than the survivor.
7. Box 15: trust assets the first spouse was entitled to benefit from.
8. Box 16: gifts with reservation made by the first spouse.
9. Box 17: box 13 + box 14 + box 15 + box 16.
10. Box 18: box 11 plus box 12 minus box 17. It can never be more than box 9.
11. Box 19: box 18 divided by box 9, multiplied by 100. Use 4 decimal places and do not round up. It can never be more than 100%.
12. Box 20: the nil rate band at the date of the second death: £325,000 for deaths from 6 April 2009 to 5 April 2031.
13. Box 21: box 20 multiplied by the box 19 percentage, rounded up to the nearest pound.

Box 22 lists any exemptions or reliefs, other than spouse exemption, that you took into account. Box 23 applies only if the first spouse was domiciled in Scotland.

Copy box 21 to IHT400 box 116 (in the simple calculation) or to box 2 of the IHT400 Calculation. The IHT400 says not to deduct it with the exemptions at boxes 92 and 93.

Worked example

These figures are invented. A widow died on 17 January 2026. Her husband died on 20 November 2008, when the nil rate band was £312,000. His will left £78,000 to their two children and everything else to her. In the 7 years before his death he had made gifts with a chargeable value of £20,000.

The exact result for box 21 is £222,916.525, which rounds up to £222,917. Her total nil rate band is £325,000 + £222,917 = £547,917 (IHT400 box 117, or box 3 of the Calculation).

Suppose her estate is £560,000 after debts and funeral costs, and passes to her nephews and nieces, so the residence nil rate band does not apply. With the claim, £12,083 is taxable and the tax is £4,833.20. Without it, £235,000 would be taxable and the tax £94,000.

Common mistakes

• Using the amount instead of the percentage. The unused amount at his death was £214,000, but what transfers is 68.5897% of the nil rate band at her death: £222,917. Using the amount would understate the claim by £8,917.
• Forgetting the first spouse's gifts. Leaving out box 10 in the example gives 75.0000% and £243,750, which is £20,833 too much (IHTM43021).
• Rounding at the wrong point. Box 19 is cut off at 4 decimal places, never rounded up. Only box 21 is rounded up to the pound.
• Putting what passed to the survivor in box 13. That is covered by spouse exemption and stays out.
• Several late spouses. Each needs its own IHT402, but the total increase is capped at 100% of the nil rate band (IHTA 1984 s.8A(5); IHTM43031). Unused shares of 60% and 70% add up to 130%, yet the transfer is limited to £325,000.
• Very old first deaths. Before 18 March 1986 the first estate fell under Capital Transfer Tax or Estate Duty, with different tax-free amounts. Before 22 March 1972 there was no spouse exemption, and until 12 November 1974 it was limited to £15,000 (IHT402 notes; IHTM43060).

Time limits and what happens next

The claim must be made within 2 years from the end of the month in which the person died, or within 3 months of the personal representatives first acting, if that ends later (IHTA 1984 s.8B(3)(a)). For a death on 17 January 2026 the 2-year date is 31 January 2028. HMRC can allow longer in some cases, such as events beyond the claimant's control (s.8B(3)(b); IHTM43009). A claim can be withdrawn up to one month after the period ends (s.8B(4)).

The claim deadline does not move the tax deadline. Tax is due by the end of the sixth month after the month of death (31 July 2026 in the example), with interest after that, so the claim normally goes in with the IHT400: see inheritance tax interest and late payment. HMRC's manual says that, close to the deadline, staff may accept a provisional claim while documents are found (IHTM43006).

A late spouse's unused residence nil rate band is claimed separately on IHT436, and its percentage can differ: see the residence nil rate band schedules IHT435 and IHT436. For the rest of the account, see how to fill in the IHT400.

Sources

• Transferring unused basic threshold for Inheritance Tax
• Inheritance Tax: claim to transfer unused nil rate band (IHT402)
• Inheritance Tax account (IHT400)
• Inheritance Tax thresholds and interest rates
• Inheritance Tax Act 1984, section 8A: transfer of unused nil-rate band between spouses and civil partners
• Inheritance Tax Act 1984, section 8B: claims under section 8A
• Inheritance Tax Act 1984, section 226: payment, general rules
• Finance Act 2026, section 72: rate bands etc for tax year 2030-31
• IHTM43001: transferable nil rate band, introduction
• IHTM43002: focus is on the extent to which the nil rate band is unused
• IHTM43005: divorce or dissolution of a civil partnership
• IHTM43006: how to make a claim
• IHTM43007: time limits
• IHTM43009: late claims
• IHTM43020: how the amount to be transferred is calculated
• IHTM43021: where there is a lifetime transfer
• IHTM43030: survivor married to more than one spouse or civil partner
• IHTM43031: limitation at 100%
• IHTM43060: first death under Estate Duty and Capital Transfer Tax
• IHTM43064: excepted estates and transferable nil rate band