The Spousal Exemption and Inheritance Tax: What Transfers Tax-Free, What Doesn't, and the Non-Domicile Trap

Introduction

The spousal exemption is one of the most powerful tools in UK inheritance tax planning—and also one of the most misunderstood. Most couples assume that when the first partner dies, everything passes to the surviving spouse without inheritance tax. This is broadly true. But that assumption masks a critical gap in many family estates: the assumption leads couples to overlook the nil-rate band, to miss opportunities to transfer unused thresholds between spouses, and to fall into the non-domicile trap that limits the exemption to just £325,000 when one partner is not UK-domiciled.

The cost of inaction is steep. A couple with a £1.2 million estate who fails to plan around these rules may trigger an unnecessary £200,000+ inheritance tax bill at the second death—money that could have been preserved with a simple will structure. For couples where one partner is not UK-domiciled, the issue is even more urgent: transfers above £325,000 are subject to 40% tax unless the non-domiciled partner makes a formal election to be treated as UK-domiciled for inheritance tax purposes.

This article explains how the spousal exemption works, where it falls short, and how to plan around its limits.

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What the Spousal Exemption Covers

Under UK inheritance tax law, transfers of value between spouses or civil partners are wholly exempt from inheritance tax [1]. This exemption applies to:

• Property and real estate (the family home, investment properties, land)
• Cash and savings (bank accounts, ISAs, premium bonds)
• Investments (shares, bonds, investment trusts, pensions)
• Business assets (shares in companies, trading assets, goodwill)
• Personal possessions (jewellery, art, cars, collections)
• Life insurance proceeds (if written in trust to the spouse)

The exemption applies equally to transfers during life (gifts) and transfers on death (via a will). It applies to married couples and to civil partners, and it applies regardless of the size of the estate—£100,000 or £5 million, the exemption is unlimited.

Who Qualifies?

The exemption applies to transfers between people who are lawfully married to each other at the time of the transfer, or who are civil partners [1]. There is no minimum duration of marriage. Transfers to former spouses (after divorce) do not qualify. Transfers to unmarried partners, even if they have been in a long-term relationship or have children together, do not qualify.

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The Unlimited Spousal Exemption vs the Nil-Rate Band: Why Giving Everything to Your Spouse Is Often a Planning Mistake

Here lies the critical distinction that catches many families off guard. The spousal exemption allows you to transfer unlimited amounts to your spouse without inheritance tax on the first death. But this does not mean the estate avoids inheritance tax forever. It merely defers it.

Each UK individual has a nil-rate band (NRB) of £325,000 [2]—an amount that can pass to any beneficiary (spouse or otherwise) without inheritance tax. When you die, your estate is taxed at 40% on the amount above your nil-rate band. If your estate is £1 million and you leave everything to your spouse, your nil-rate band is unused—wasted.

The Two-Death Problem

When the second spouse dies, their estate will have £325,000 of their own nil-rate band, but your unused £325,000 is lost forever. The surviving spouse's estate is then taxed at 40% on every pound above £325,000. On a £1.2 million joint estate, the inheritance tax bill at the second death could be around £350,000.

Compare this to a couple who structures their first death around the nil-rate band: the first spouse uses their full £325,000 NRB in a discretionary trust, and leaves the remainder to the surviving spouse exempt. When the second spouse dies, their estate has £325,000 of their own NRB plus the £325,000 in the trust (which is not part of their taxable estate). The surviving spouse's executors can then claim to transfer the unused nil-rate band from the first spouse's estate, doubling the second estate's available threshold. The inheritance tax bill falls dramatically.

Residence Nil-Rate Band (RNRB)

There is a second nil-rate band available to those who leave a qualifying residence (a home) to direct descendants (children, grandchildren, etc.). This Residence Nil-Rate Band (RNRB) is £175,000 [2], available in addition to the standard £325,000 NRB. Like the basic NRB, if you leave everything to your spouse, you risk wasting your RNRB. And like the basic NRB, any unused RNRB can be transferred to a surviving spouse [3]—but only if the claim is made within two years of the first death and only if the first spouse's personal representative acts on it.

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The Non-UK Domicile Restriction: The £325,000 Cap

This is where the spousal exemption shows its teeth. If one partner in a marriage is not domiciled in the UK (and has not made an election to be treated as UK-domiciled), the unlimited spousal exemption does not apply. Instead, transfers to the non-domiciled spouse are capped at £325,000 [4]—the current nil-rate band.

Who Is "Non-Domiciled"?

For inheritance tax purposes, domicile is a technical term. You are domiciled in the UK if:

• You are resident in the UK and intend to remain indefinitely, or
• The UK is your country of origin and you have not acquired a new permanent home elsewhere

Important change from April 6, 2025: The inheritance tax rules on domicile have been reformed. From this date, long-term UK residence replaces domicile for inheritance tax purposes [4]. You are treated as UK long-term resident if you have been UK resident for at least 15 of the previous 20 tax years. This change benefits many non-UK nationals who have lived in the UK for extended periods—they will now have access to the unlimited spousal exemption without needing to make an election.

The £325,000 Cap: How It Works

Imagine one spouse is a non-domiciled US citizen living in the UK on a work visa. When the UK-domiciled spouse dies with an estate of £1 million, only £325,000 passes to the non-domiciled spouse exempt. The remaining £675,000 is subject to 40% inheritance tax—a £270,000 bill. This is a severe shock to many families.

The Deemed Domicile Election

The non-domiciled spouse can avoid this trap by making a formal election to be treated as UK-domiciled for inheritance tax purposes [5]. This election can be made:

• During the life of the non-domiciled spouse, at any time, and takes effect from the date stated in the election
• After the death of a UK-domiciled spouse, by the surviving spouse's personal representatives within two years of the death

Once the election is made, the non-domiciled spouse is treated as UK-domiciled for all inheritance tax purposes going forward. The election cannot be revoked, and it affects not only the inheritance tax treatment of assets received from the first spouse, but also the non-domiciled spouse's own estate when they die. Crucially, this means the non-domiciled spouse becomes liable to inheritance tax on their worldwide assets (not just UK assets) on their own death—a significant change in their tax position.

Important timing note: For couples where the non-domiciled partner was non-domiciled before April 6, 2025, the old rules apply, but transitional rules allow elections made before that date to continue to have effect under the new long-term residency regime [6].

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Transferring Unused Nil-Rate Band and RNRB to the Surviving Spouse

One of the most valuable but underutilized features of modern UK inheritance tax law is the ability to transfer unused thresholds from the first spouse to die to the surviving spouse.

How It Works

If the first spouse does not use their full nil-rate band (or RNRB), the unused portion can be transferred to the surviving spouse [2]. The transfer is calculated as a percentage of the unused allowance, not a fixed amount. For example:

• First spouse's nil-rate band at death: £325,000
• Assets passing to surviving spouse: £250,000
• Unused NRB: £75,000
• Percentage unused: 23%

When the surviving spouse later dies, they have 123% of the standard nil-rate band available to them (their own 100% plus the transferred 23%), which equates to £398,750 instead of the standard £325,000.

Critical Deadlines and Requirements

The transfer does not happen automatically. It must be claimed by the personal representative (executor) of the first spouse's estate within two years of the death [2]. If the two-year deadline passes without a claim, the unused threshold is lost forever.

To make the claim, the personal representative must file the appropriate form with the inheritance tax return (IHT400):

• Form IHT402 (for all estates)
• Form IHT217 (for excepted estates where the whole nil-rate band is available to transfer)
• Form IHT436 (to transfer unused RNRB)

Transferring the RNRB

The same principle applies to the Residence Nil-Rate Band. If the first spouse did not use their full RNRB (often because they did not own a qualifying home, or because they left it to someone other than direct descendants), the unused portion can be transferred [3]. Again, the transfer is expressed as a percentage, and the deadline is two years from the date of death.

Practical note: If the first spouse left their home to direct descendants but also left assets to the surviving spouse, the RNRB may have been only partially used. The personal representatives should calculate the unused percentage carefully and claim it on the IHT436 form.

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Planning for the Second Death: Why the Spousal Exemption Merely Defers Tax

The spousal exemption is not a permanent tax shield—it is a deferral. When the surviving spouse dies, their entire estate (including assets inherited from the first spouse, plus any assets of their own) becomes taxable. If proper planning was not in place at the first death, the surviving spouse's estate can face a catastrophic tax bill.

The Role of the Discretionary Trust

The most common and effective planning tool is the nil-rate band discretionary trust [7]. Under this structure:

1. On the first spouse's death, their will leaves £325,000 (their nil-rate band) to a discretionary trust for the benefit of the surviving spouse, children, and grandchildren.
2. The trust uses up the first spouse's nil-rate band but the assets remain outside the surviving spouse's taxable estate (because the surviving spouse is only a discretionary beneficiary, not the outright owner).
3. The surviving spouse receives the remainder of the estate outright, exempt under the spousal exemption.
4. When the surviving spouse dies, the discretionary trust assets are not part of their estate, so they are not taxed. The surviving spouse's own nil-rate band can be used against their remaining assets.
5. The surviving spouse's personal representatives can claim to transfer any unused nil-rate band from the first spouse's estate, further increasing the second estate's available threshold.

This structure requires no cost to implement (it is simply a will provision), but it can save hundreds of thousands of pounds in inheritance tax.

Why Not Gifting Strategies?

Some couples attempt to reduce the taxable estate by gifting money during life. Under current inheritance tax law, gifts are subject to a seven-year rule: gifts made more than seven years before death are exempt, but gifts made within seven years may be subject to tax. For most couples, this is too slow and uncertain a strategy. A discretionary trust on first death is immediate and certain.

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Worked Example 1: A Standard UK Couple

The Situation

• Married couple, both UK-domiciled
• Joint estate: £1.2 million (home £600k, savings £300k, investments £300k)
• Two adult children
• Home will pass to surviving spouse, then to children

Without Planning (All to Surviving Spouse)

First death (assume spouse A dies):

• Estate: £1.2m
• Left to spouse B (exempt): £1.2m
• Inheritance tax due: £0

Second death (spouse B dies):

• Estate: £1.2m
• Nil-rate band available: £325,000
• Taxable amount: £1.2m - £325,000 = £875,000
• Inheritance tax due: £875,000 × 40% = £350,000

With Planning (NRB Trust on First Death)

First death (spouse A dies):

• Estate: £1.2m
• To discretionary trust (NRB): £325,000
• To spouse B (exempt): £875,000
• Inheritance tax due: £0

Second death (spouse B dies):

• Spouse B's own estate: £875,000 + growth
• Spouse B's available NRB: £325,000
• Plus transferred NRB from spouse A: £325,000 (because spouse A's trust assets are outside spouse B's estate)
• Taxable amount: £875,000 - £325,000 = £550,000
• Inheritance tax due: £550,000 × 40% = £220,000

Tax saving: £130,000

If the surviving spouse also owns a qualifying home and passes it to direct descendants, they can also transfer any unused RNRB from the first spouse's estate, saving a further £70,000 (£175,000 × 40%).

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Worked Example 2: A Mixed-Domicile Marriage

The Situation

• Married couple: spouse A is UK-domiciled; spouse B is US-domiciled (non-UK resident, no UK domicile under old rules)
• Joint estate: £800,000 (home £450k, savings £350k)
• Both spouses are in their mid-60s
• Spouse B has not made a domicile election

Without Planning (All to Non-Domiciled Spouse)

Spouse A dies:

• Estate: £800,000
• To spouse B (capped at NRB, non-domiciled spouse exemption limited): £325,000 exempt
• To spouse B (taxable): £475,000
• Inheritance tax due: £475,000 × 40% = £190,000

This is a shock: nearly a quarter of the estate goes to tax, and the non-domiciled spouse receives only £610,000 of the £800,000 estate (£325,000 exempt + £285,000 after tax).

With Planning (Spouse B Makes Domicile Election)

Spouse B makes an election to be treated as UK-domiciled for inheritance tax purposes (either before spouse A dies, or within two years after, via the personal representatives).

Spouse A dies:

• Estate: £800,000
• To spouse B (now treated as UK-domiciled, unlimited exemption): £800,000 exempt
• Inheritance tax due: £0

When spouse B dies (now UK-domiciled):

• Estate: £800,000 + growth + spouse B's own assets
• Spouse B now liable to inheritance tax on worldwide assets (not just UK assets)
• But the unlimited spousal exemption applies to the inherited £800,000

The election requires careful planning, because it also means spouse B's worldwide assets (e.g., US property, US bank accounts) become liable to UK inheritance tax on spouse B's death. But for many couples, this trade-off is worthwhile: it eliminates the 40% tax hit on the first death and provides unlimited spousal exemption, more than offsetting the broader tax exposure on the second death.

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Frequently Asked Questions

Q1: Does the spousal exemption apply to unmarried partners?

No. The exemption applies only to married couples and civil partners. This is a gap in the law that catches many cohabiting couples. An unmarried partner has no spousal exemption, and inherits only within the scope of their own nil-rate band (£325,000 exempt, the remainder taxed at 40%). For couples in long-term relationships but not married, marriage is the most straightforward inheritance tax planning tool.

Q2: If we live abroad, can we still use the spousal exemption?

Yes, the spousal exemption applies regardless of where you live. What matters for inheritance tax purposes is domicile (or from April 6, 2025, long-term UK residence), not residence. If you are both domiciled outside the UK, you are not liable to UK inheritance tax (except on UK-situs assets like UK property). If one spouse is UK-domiciled (or UK long-term resident) and the other is not, the non-domiciled spouse faces the £325,000 cap unless they make an election.

Q3: Can we transfer unused thresholds if we did not claim them within two years?

No. The two-year deadline is strict, and there is no provision to extend it. If the deadline passes without a claim, the unused threshold is lost. The only exception is if the personal representative can demonstrate a reasonable excuse for delay, but this is rarely accepted by HMRC. It is vital to ensure that the personal representatives understand the deadline and make the claim promptly.

Q4: If our estate is below the nil-rate band, do we need to worry about any of this?

If your combined estate is below £325,000 per spouse (£650,000 total), you will have no inheritance tax liability even without planning, assuming the assets pass to a spouse or within a nil-rate band. However, many estates can grow unexpectedly through life insurance proceeds, pension death benefits, or property appreciation. It is worth reviewing your plan at least every five years, and especially if you receive a large inheritance or windfall.

Q5: What happens to the spousal exemption if we have children from previous relationships?

The spousal exemption still applies to transfers between the current spouses. However, if you want to ensure that some of your estate goes to your children from a previous relationship (not to your current spouse), you should use a will that splits your estate. A common structure is to leave your nil-rate band (£325,000) to your children or to a trust for your children, and the remainder to your current spouse. This ensures your children receive something and also makes use of your nil-rate band. The remaining spouse's exemption still applies to the assets left to them.

Q6: Can we use the spousal exemption for lifetime gifts?

Yes. If you gift assets to your spouse during your life, the gift is exempt under the spousal exemption, provided you remain married. This can be useful for income tax or capital gains tax planning (e.g., to rebalance assets so income falls on the lower-earning spouse). There is no limit to the amount you can gift to your spouse during life, and the gift is not a transfer of value for inheritance tax purposes.

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Disclaimer

This article is general information only and does not constitute legal or tax advice. The law on inheritance tax is complex and changes periodically. Figures quoted (the £325,000 nil-rate band, the £175,000 RNRB) are correct as of April 2026 and are frozen at these levels until April 2028, but are subject to change. The rules on domicile are changing from April 6, 2025, and the rules on non-domiciled spouses are being reformed.

You should not rely on this article alone to make decisions about your estate or to structure your will. Every family's circumstances are different, and what works for one couple may not work for another. Before making any changes to your will or estate plan, you should consult with a qualified solicitor or tax advisor who specializes in inheritance tax planning.

The references in this article are correct as of April 28, 2026.