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For unmarried couples, however, each estate is treated entirely separately, with no automatic tax relief between them.
Key Takeaways
- Unmarried couples are taxed as two separate estates with no spouse exemption
- For married couples, the older spouse is usually deemed to have died first
- Assets pass to the surviving spouse before inheritance tax is calculated
- The second estate is then assessed in the normal way
- Proper estate planning can preserve allowances and reduce tax significantly
Unmarried Couples: No Automatic Tax Protection
Where a cohabiting couple die together, each individual’s estate is assessed separately for inheritance tax purposes.
There is no spouse exemption and no ability to restructure matters after death. Inheritance tax cannot be mitigated retrospectively.
This means that if both estates exceed the available nil-rate bands, tax may arise in both cases.
Married Couples: The “Commorientes” Rule
Where a married couple die in the same accident and the order of death cannot be determined, UK law applies what is commonly referred to as the “commorientes” rule.
In simple terms:
The older spouse is deemed to have died first.
This means their estate passes under their will to the surviving spouse. Transfers between spouses are generally exempt from inheritance tax.
The second spouse’s estate is then assessed for inheritance tax in the normal way.
If there is medical evidence showing one spouse survived longer – even by hours or days – then the actual order of death will apply instead.
Why the Order of Death Matters
The sequencing can have material consequences:
- It determines whether the spouse exemption applies
- It affects how the nil-rate band and residence nil-rate band are used
- It influences whether transferable allowances are available
- It impacts how trusts in the will operate
Without structured planning, families can unintentionally lose tax allowances that would otherwise have been preserved.
With appropriate estate planning in place, married couples can often secure significant tax savings, in many cases exceeding £100,000, purely through correct will structuring, before any additional inheritance tax planning is considered.
Planning Is Put in Place Before, Not After
A common misunderstanding is that inheritance tax can be “sorted out” after death.
It cannot. Once a person has died any IHT payable is due. There is nothing that can be done retrospectively for that estate. However, deeds of variation can change the will to save IHT for any beneficiary of the deceased person.
The structure of the wills, ownership of assets and trust provisions must already be in place. Once both individuals have died, no further planning can be introduced.
This is why proactive estate planning is essential, particularly for couples whose estates exceed available tax thresholds.
What Is Often Overlooked
- Cohabiting couples do not benefit from spouse exemptions
- The law defaults to the older spouse dying first if timing is unclear
- The second estate carries the inheritance tax assessment
- Proper will structuring can materially reduce exposure
Conclusion
If a couple die together, inheritance tax treatment depends heavily on their marital status and the legal order of death.
Unmarried couples are assessed entirely separately. Married couples benefit from the spouse exemption, with the older spouse usually deemed to have died first where timing is uncertain.
The tax outcome is determined by the structure already in place. Planning early – rather than assuming matters can be resolved later – is what protects family wealth.
If you need any help or advice in this complex area please contact us as soon as possible.
Disclaimer. The information in this article is general in nature and does not constitute personal financial, tax, or legal advice. UK tax legislation changes frequently, and the specific application of any rule or strategy depends on individual circumstances. Figures, thresholds, and reliefs mentioned are correct as of the 2026 to 2027 tax year unless otherwise stated. Before acting on any information here, consult a qualified adviser who has reviewed your full situation. Bluebond Tax Planning provides personal recommendations only under a signed client agreement, following a full review. Bluebond Tax Planning operates under UK legal frameworks and recognised professional conduct standards. Tax planning and legal work are not FCA regulated.
