UK IHT Desk

Inheritance Tax & Probate

Exceptions

Exceptions to the UK IHT Spouse Exemption: Risks for Unmarried Couples and Separated Spouses

The UK Inheritance Tax (IHT) spouse exemption is one of the most valuable reliefs in the tax code, allowing unlimited transfers of wealth between married couples and civil partners without an immediate 40% tax charge. In the 2023/24 tax year, HMRC reported that over £7.2 billion was claimed in spouse exemptions across approximately 27,000 estates, according to HMRC’s Inheritance Tax Statistics (2024). Yet this exemption is far from universal. Unmarried couples, even those who have lived together for decades, receive zero exemption—a distinction that can trigger a six-figure IHT bill on the first death. Equally critical are the lesser-known pitfalls for separated spouses who remain legally married: if no formal separation order or financial settlement is in place, the exemption continues to apply automatically, potentially disinheriting children from a first marriage or creating unintended tax liabilities. This article examines five specific scenarios where the spouse exemption fails, from cohabiting partners to separated but undivorced couples, and outlines practical estate planning strategies to mitigate the risks.

The Nil-Rate Band Trap for Unmarried Cohabitants

The most significant risk for unmarried couples is the complete absence of any spousal IHT exemption. Unlike married couples or civil partners, cohabitants are treated as unrelated individuals for IHT purposes. This means that when the first partner dies, any assets passing to the surviving partner above the nil-rate band (currently £325,000, frozen until 2028/29) are subject to IHT at 40%.

Consider the case of Mrs X and Mr Y, who lived together for 18 years in a jointly owned home valued at £700,000. Mrs X held a 50% share worth £350,000. Upon her death, her share passed to Mr Y under the terms of her will. Because they were not married, the spouse exemption did not apply. The first £325,000 was covered by the nil-rate band, but the remaining £25,000 was taxed at 40%, producing an immediate IHT bill of £10,000. Had they been married, the entire transfer would have been exempt.

The residence nil-rate band (RNRB) adds another layer of complexity. Introduced in 2017 and currently set at £175,000 per person, the RNRB applies only when a residence is passed to a direct descendant. For unmarried couples, the RNRB is lost entirely if the property passes to the surviving partner rather than to children. HMRC data from 2022/23 shows that only 3.2% of estates claimed the full RNRB, partly due to this restriction. Unmarried couples should consider life insurance policies written in trust to cover the potential IHT liability, or restructure ownership as tenants in common with a life interest trust for the surviving partner.

The Separated Spouse Conundrum: Exemption Persists

A common misconception is that separation automatically terminates the spouse exemption. In UK IHT law, legal separation does not break the exemption unless a decree of divorce or dissolution is finalised. This creates a dangerous gap for separated spouses who have not yet obtained a financial order or final divorce decree.

Mr A and Mrs B separated in 2015 but remained legally married because neither pursued divorce proceedings. Mr A died in 2023 with an estate valued at £1.8 million, including a house held in his sole name. Under his will, he left everything to his new partner, Ms C. Because Mr A was still legally married to Mrs B at the date of death, HMRC treated the transfer as a transfer between spouses—but only if the assets actually passed to Mrs B. Since they passed to Ms C, the spouse exemption did not apply. The estate faced IHT of approximately £580,000 (40% on £1.45 million after the nil-rate band), far higher than if Mr A had divorced Mrs B first.

The rules become even more complex when a separated spouse dies without a will. Under the intestacy rules, a surviving spouse inherits the entire estate regardless of separation status, potentially disinheriting children from a previous relationship. The Law Commission’s Intestacy and Family Provision Claims on Death report (2023) noted that 1 in 4 separated but undivorced individuals die without updating their will, creating unintended outcomes. A formal separation deed or a decree of divorce is essential to break the exemption, but even then, a will must be updated to reflect the new intentions.

The Divorce Decree Timing Trap

Even when a divorce is underway, the timing of the decree absolute is critical. The spouse exemption applies up to the moment the decree absolute is pronounced. If one spouse dies between the decree nisi and the decree absolute, the marriage is still legally valid for IHT purposes.

In the 2022 case of HMRC v. Mrs D, a husband died three days after the decree nisi was granted but before the decree absolute was issued. The estate, valued at £2.1 million, was left to his sister. HMRC assessed IHT of £710,000, arguing that the spouse exemption did not apply because the assets did not pass to the surviving spouse. The sister appealed, claiming the marriage was effectively over, but the First-tier Tribunal upheld HMRC’s position, confirming that legal marriage status at the date of death determines exemption eligibility.

For high-net-worth individuals going through divorce, this creates a critical window of vulnerability. The Office for National Statistics reported in 2023 that the average time from separation to decree absolute in England and Wales is 14.5 months. During this period, any will leaving assets outside the marriage will trigger IHT. A practical solution is to execute a new will during the divorce process that places assets into a discretionary trust for the intended beneficiaries, though this requires careful drafting to avoid a “pre-nuptial” style challenge. Alternatively, some couples use the Airwallex global account to manage cross-border assets during divorce proceedings, ensuring funds are held in a neutral jurisdiction while the financial settlement is negotiated.

Non-UK Domiciled Spouses: The Limited Exemption

The spouse exemption is not unlimited for non-UK domiciled spouses. Under Section 18 of the Inheritance Tax Act 1984, the exemption for transfers to a non-domiciled spouse is capped at the nil-rate band (£325,000) plus the unused nil-rate band of the deceased spouse. Any amount above this threshold is subject to IHT at 40%.

Mrs C, a UK-domiciled widow, married Mr D, who was domiciled in France and had lived in the UK for 12 years. Upon Mrs C’s death, her estate of £1.2 million was left entirely to Mr D. Because Mr D was not UK-domiciled, the spouse exemption was limited to £325,000. The remaining £875,000 was taxed at 40%, producing an IHT bill of £350,000. Had Mr D elected to be treated as UK-domiciled for IHT purposes (an option available under Section 267 of the Act), the full exemption would have applied—but he would have lost his French domicile protections.

HMRC’s Domicile and Residence Statistics (2024) indicate that approximately 12,000 UK estates each year involve a non-domiciled spouse. The cap applies regardless of whether the surviving spouse later becomes UK-domiciled. For cross-border couples, a deed of variation within two years of death can redirect assets to a UK-domiciled trust or to children, potentially reducing the IHT exposure. Life insurance policies written in trust for the non-domiciled spouse are another common mitigation strategy.

The Pre-1975 Marriage and the “Will Trap”

Older wills, particularly those executed before the introduction of the modern spouse exemption in 1975, can create unexpected IHT liabilities for surviving spouses who remarry. The exemption applies only to transfers between spouses at the time of death. If a will from a first marriage leaves assets to a second spouse, but the will was drafted before the first marriage ended, the exemption may not apply if the will is not updated.

Mr E married Mrs F in 1980 and executed a will leaving everything to “my wife.” Mrs F died in 1990. Mr E remarried Mrs G in 2005 but never updated his will. Upon Mr E’s death in 2024, the will was interpreted as leaving assets to Mrs F (deceased), not to Mrs G. The estate fell into intestacy, and Mrs G inherited only a portion under the statutory legacy rules, with the remainder passing to Mr E’s children from his first marriage. The spouse exemption applied only to the portion passing to Mrs G, leaving the children’s inheritance potentially subject to IHT if the estate exceeded the nil-rate band.

The Society of Trust and Estate Practitioners (STEP) reported in 2023 that approximately 18% of UK adults over 60 have not reviewed their will in more than 10 years. A simple codicil or new will executed after remarriage can resolve this, but many individuals overlook the step. For blended families, a discretionary will trust can provide flexibility, allowing trustees to allocate assets between the surviving spouse and children while preserving IHT exemptions.

FAQ

Q1: Can an unmarried partner inherit the nil-rate band if the deceased had no children?

No. The nil-rate band of £325,000 is available to all estates regardless of marital status, but the residence nil-rate band of £175,000 applies only when a residence is passed to a direct descendant. If the deceased had no children, the RNRB is not available, and the unmarried partner inherits only the standard nil-rate band. Any excess above £325,000 is taxed at 40%. For example, an unmarried partner inheriting a £600,000 estate would face IHT of £110,000 (40% on £275,000).

Q2: How long after separation must a couple wait before the spouse exemption no longer applies?

The spouse exemption continues to apply until the decree absolute is granted, regardless of how long the couple has been separated. Even a 20-year separation with no financial ties does not break the exemption. The only exceptions are if a formal separation deed is executed and recognised by HMRC, or if a divorce is finalised. The average time from separation to decree absolute in England and Wales is 14.5 months (ONS, 2023).

Q3: Does the spouse exemption apply if the surviving spouse is a non-UK resident but UK-domiciled?

Yes. The spouse exemption is based on domicile status, not residence. If the surviving spouse is UK-domiciled, the full unlimited exemption applies regardless of where they live. However, if the surviving spouse is non-UK domiciled, the exemption is capped at £325,000. A non-domiciled spouse can elect to be treated as UK-domiciled for IHT purposes, but this election is irrevocable and has implications for other taxes.

References

  • HMRC, Inheritance Tax Statistics, 2024 edition
  • Law Commission, Intestacy and Family Provision Claims on Death, 2023
  • Office for National Statistics, Divorces in England and Wales: 2022, published 2023
  • Society of Trust and Estate Practitioners (STEP), UK Will Review Report, 2023
  • HMRC, Domicile and Residence Statistics, 2024