Key facts
- The unused percentage of the first spouse’s NRB can be transferred to the surviving spouse’s estate.
- The maximum transferable NRB is 100%, giving a combined threshold of up to £650,000 (2 × £325,000).
- The transfer is based on the percentage unused, not the cash amount — so it benefits from any increase in the NRB.
- A claim must be made by the personal representatives of the surviving spouse’s estate using form IHT402.
- The claim must be made within 2 years of the end of the month of the second death (or 3 months after the grant of probate, if later).
What Is the Transferable Nil-Rate Band?
The transferable nil-rate band (TNRB) allows the unused proportion of one spouse’s or civil partner’s nil-rate band to be transferred to the estate of the surviving spouse when they later die. This effectively allows married couples and civil partners to combine their NRBs.[1]
For 2025/26, the NRB is £325,000 per person. If the first spouse’s NRB was entirely unused (e.g. because everything passed to the surviving spouse under the spouse exemption), the surviving spouse’s estate can claim an additional £325,000 — giving a combined IHT-free threshold of £650,000.
How the Transfer Works
The TNRB is based on the percentage of the NRB unused by the first spouse, not the cash amount:[2]
- Calculate what percentage of the first spouse’s NRB was unused at their death
- Apply that percentage to the NRB in force when the surviving spouse dies
- Add the result to the surviving spouse’s own NRB
Example: John died in 2005 when the NRB was £275,000. He left £55,000 to his children and the rest to his wife Mary. He used 20% of his NRB (£55,000 ÷ £275,000). When Mary dies in 2026, 80% of the current NRB can be transferred: 80% × £325,000 = £260,000. Mary’s estate has a combined threshold of £325,000 + £260,000 = £585,000.
Why Percentages Matter
The percentage basis is important because the NRB can change over time. If the first spouse died when the NRB was lower, the percentage approach means the transfer benefits from any increase in the NRB by the time the surviving spouse dies.[2]
| Scenario | First Death NRB | % Unused | Second Death NRB | Amount Transferred | Combined Threshold |
|---|---|---|---|---|---|
| 100% unused | £275,000 | 100% | £325,000 | £325,000 | £650,000 |
| 50% unused | £300,000 | 50% | £325,000 | £162,500 | £487,500 |
| 75% unused | £263,000 | 75% | £325,000 | £243,750 | £568,750 |
Making the Claim
The claim is made by the personal representatives of the surviving spouse’s estate using form IHT402 (a schedule to the IHT400). The claim must include:[3]
- A copy of the death certificate of the first spouse
- A copy of the grant of probate (or letters of administration) for the first spouse’s estate
- A copy of the first spouse’s will (if applicable)
- Details of any IHT paid on the first spouse’s estate
- Calculation of the unused percentage
Claim Deadline
The claim must be made within 2 years of the end of the month of the surviving spouse’s death, or 3 months after the grant of probate/letters of administration for the surviving spouse’s estate (whichever is later).[2]
HMRC has discretion to accept late claims in exceptional circumstances, but this is not guaranteed.
Multiple marriages: If the surviving spouse was widowed more than once, unused NRB can be claimed from each predeceased spouse. However, the maximum transfer is capped at 100% of the NRB in force at the survivor’s death. Even if three deceased spouses each left 100% unused, the maximum additional NRB is £325,000.
RNRB Transfer
The residence nil-rate band (RNRB) can also be transferred in the same way. If the first spouse did not use their RNRB (e.g. because they did not own a qualifying home at death), the unused percentage can be claimed by the surviving spouse’s estate, giving a potential combined RNRB of up to £350,000.[1]
Frequently Asked Questions
How does the transferable nil-rate band work?
When the first spouse dies and leaves everything to the surviving spouse (exempt transfer), their NRB is 100% unused. When the surviving spouse later dies, their personal representatives can claim that unused percentage. If the NRB is £325,000, the claim adds another £325,000, giving a combined threshold of £650,000.
What if the first spouse used part of their NRB?
Only the unused percentage transfers. For example, if the first spouse used 40% of their NRB (through gifts or legacies to non-exempt beneficiaries), only 60% transfers. At the current NRB of £325,000, that would be £195,000 — giving a combined threshold of £520,000.
Can I claim from more than one deceased spouse?
Yes, if someone has been widowed more than once, the PRs can claim unused NRB from previous spouses. However, the total transferred cannot exceed 100% of the NRB in force at the survivor’s death — so the maximum combined threshold is always 2 × the current NRB.
Does the RNRB also transfer?
Yes. The unused percentage of the residence nil-rate band (RNRB) can also transfer to the surviving spouse’s estate in the same way. This means a married couple can potentially have a combined IHT-free threshold of £1,000,000 (£650,000 NRB + £350,000 RNRB).
Further Reading
- The Nil-Rate Band (£325,000) — the tax-free threshold in detail
- The Residence Nil-Rate Band — the additional £175,000 allowance
- Spouse & Civil Partner Exemption — the unlimited spouse exemption
- The IHT400 Form — submitting the IHT402 schedule
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