Cohabiting Couples and Tax: The Legal Differences From Marriage in 2026/27
Cohabiting couples in the UK get none of the tax reliefs available to married couples and civil partners in 2026/27 — no Marriage Allowance, no unlimited spousal IHT exemption, no automatic CGT no gain/no loss transfers.
"Common law marriage" is a myth in UK tax law
One of the most persistent misconceptions in UK personal finance is the idea of "common law marriage" — the belief that living together for long enough, or having children together, creates marriage-equivalent legal rights. It does not. UK tax law draws a hard line between married couples and civil partners on one side, and cohabiting couples — however long-term and committed — on the other.
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The Marriage Allowance lets one partner transfer £1,260 of their unused Personal Allowance to their spouse or civil partner, worth up to £252 a year in tax saved (20% of £1,260) in 2026/27. It is only available where the couple are legally married or in a registered civil partnership — cohabiting couples cannot claim it under any circumstances, regardless of how long they have lived together or shared finances.
Capital Gains Tax: no automatic transfers between cohabiting partners
Married couples and civil partners can transfer assets between themselves at any time on a "no gain, no loss" basis, meaning no Capital Gains Tax arises on the transfer itself. Cohabiting couples get no such treatment: if one partner transfers an asset that has grown in value — a share portfolio, a second property, a business interest — to the other, it is treated exactly as if it had been sold to an unrelated third party at market value, potentially triggering Capital Gains Tax on the transferring partner even though no money changed hands.
Inheritance Tax: no unlimited spousal exemption
Transfers between married couples and civil partners, whether during life or on death, are completely exempt from Inheritance Tax, with no upper limit. There is no equivalent exemption for cohabiting couples. If a cohabiting partner dies and leaves assets to their surviving partner (assuming a will exists — see below), the value is fully within the estate for Inheritance Tax purposes, using up the standard £325,000 nil-rate band and, potentially, the Residence Nil-Rate Band of up to £175,000 if the estate qualifies, in exactly the same way as a gift to a friend or distant relative would.
inheritance-tax-ukThe one place cohabiting couples are treated the same: means-tested benefits
Interestingly, the position reverses for means-tested benefits such as Universal Credit. HMRC and DWP treat a cohabiting couple living together as if they were married for benefit assessment purposes, meaning both partners' income and savings are assessed jointly — exactly as they would be for a married couple. This can work against cohabiting couples in a benefits context even though it works against them in the opposite direction for the tax reliefs described above.
Practical steps for cohabiting couples
Because none of the automatic protections apply, cohabiting couples who want similar outcomes to a married couple generally need to arrange them deliberately:
- Write a will — without one, a surviving partner has no automatic inheritance rights at all
- Consider a cohabitation agreement — setting out how assets and finances would be divided if the relationship ends
- Review property ownership — holding a home as "joint tenants" (automatic survivorship) versus "tenants in common" (each partner's share passes according to their will) has very different consequences
- Consider life insurance written in trust — to provide for a partner without adding to the Inheritance Tax position
Bottom line
Cohabiting, however long-term, does not create the tax reliefs marriage and civil partnership provide in the UK. From the Marriage Allowance to Capital Gains Tax transfers to the unlimited spousal Inheritance Tax exemption, cohabiting couples are treated as legal strangers for tax purposes — while being treated as a single household for means-tested benefits. Understanding this asymmetry is the first step to protecting a cohabiting partner properly.
Sources
- GOV.UK: Marriage Allowance
- GOV.UK: How Inheritance Tax works: thresholds, rules and allowances
- Citizens Advice: Living together and marriage — legal differences
Frequently asked questions
Do cohabiting couples get the Marriage Allowance?
No. The Marriage Allowance, worth up to £252 a year in 2026/27, is only available to married couples and registered civil partners — living together, however long-term the relationship, does not qualify.
Is there a 'common law marriage' in UK tax law?
No — 'common law marriage' has no legal status in the UK for tax or most other legal purposes, regardless of how long a couple has lived together or whether they have children. Only formal marriage or civil partnership carries the associated tax reliefs.
Can cohabiting couples transfer assets to each other without Capital Gains Tax?
No. Married couples and civil partners can transfer assets between themselves at any time on a no gain/no loss basis; cohabiting couples cannot — any transfer of an asset that has grown in value can trigger Capital Gains Tax on the transferring partner, exactly as if it were sold to a stranger.
What happens to Inheritance Tax if a cohabiting partner dies without a will?
A surviving cohabiting partner has no automatic entitlement to inherit under intestacy rules (the rules that apply when someone dies without a will), and any inheritance they do receive, whether by will or otherwise, does not benefit from the unlimited spousal Inheritance Tax exemption that married couples and civil partners get.
Does cohabiting affect Universal Credit differently from marriage?
No — for means-tested benefits like Universal Credit, HMRC and DWP treat a cohabiting couple living together as if married, meaning both incomes and savings are assessed jointly regardless of legal status. This is the opposite of the tax reliefs above, where cohabiting couples get less favourable treatment, not more.
What can cohabiting couples do to protect themselves?
Writing a will, considering a cohabitation agreement, and reviewing property ownership (joint tenants vs tenants in common) are the main practical steps, since none of the automatic protections married couples and civil partners get apply to cohabiting couples by default.
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Related reading
Civil Partnership vs Marriage: Are There Any Tax Differences in 2026/27?
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Marriage and Civil Partnership Tax Benefits in the UK 2026/27 — A Complete Overview
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