Transferring Unused IHT Nil Rate Band Between Spouses — How It Works

The Spousal Exemption — Unlimited and Automatic

Any assets transferred between UK-domiciled spouses or civil partners are completely exempt from inheritance tax, regardless of value. This means when a husband, wife or civil partner dies, the entire estate can pass to the surviving partner with no IHT bill at all.

However, this simply defers the tax — when the surviving spouse eventually dies, the full combined estate (minus allowances) becomes subject to IHT. Planning ahead for that second death is therefore critical.

Transferable Nil Rate Band

When assets pass between spouses and no IHT arises on the first death, any unused proportion of the deceased's nil rate band (£325,000) can be transferred to the surviving spouse's estate. HMRC calls this the transferable nil rate band (TNRB).

If the first spouse's entire NRB was unused (i.e. everything was left to the survivor), 100% of the NRB transfers. The survivor's estate can then benefit from up to £650,000 in NRB on their death.

Historical Estates Qualify Too

The transfer applies even if the first death occurred before the TNRB rules were introduced in October 2007. Provided the marriage was intact at the first death and assets were not fully used against the NRB, the survivor's estate can claim the transfer — often a welcome discovery for families dealing with an elderly surviving parent's estate.

Transferable Residence Nil Rate Band

The same principle applies to the residence nil rate band (RNRB, £175,000). Unused RNRB from the first death transfers to the second estate. Because the RNRB was introduced in April 2017, the transfer also applies where the first death was before that date — HMRC treats the first death as having had a 100% unused RNRB available.

In practice, a surviving spouse who dies leaving a qualifying home to direct descendants could benefit from £350,000 in RNRB — on top of £650,000 in NRB — shielding a total of £1,000,000 from IHT.

Worked Example

Peter died in 2018, leaving everything to his wife Ann. His entire NRB (£325,000) and RNRB were unused. Ann dies in 2026 leaving an estate worth £950,000, including her main home, to her adult children.

• Ann's own NRB: £325,000
• Transferred NRB from Peter: £325,000
• Ann's own RNRB: £175,000
• Transferred RNRB from Peter: £175,000
• Total threshold: £1,000,000

Ann's estate of £950,000 falls below the combined threshold. IHT bill: £0.

How to Claim the Transfer

The transfer is not automatic — the executor of the surviving spouse's estate must claim it on the IHT402 form (for the NRB transfer) and IHT436 (for the RNRB transfer), filed alongside the main IHT400. Evidence of the first spouse's death and their estate position will be required.

Domicile Matters

The full spousal exemption only applies where both spouses are UK-domiciled. If the surviving spouse is non-UK domiciled, the exemption is capped (currently at £325,000). Cross-border families should take specialist advice.

Use our [Inheritance Tax Calculator](/inheritance-tax-calculator) to model the combined NRB and RNRB position for a surviving spouse's estate.

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