Core takeaway: Marriage/civil partnership unlocks tax reliefs, pension rights, inheritance protections and death‑benefit rules that do not apply to unmarried partners. The financial difference can easily exceed £200,000–£500,000 over a lifetime, mainly due to inheritance tax and pension survivorship.
1. Inheritance Tax (IHT) Spousal Exemption — Unlimited
All assets left to a spouse/civil partner are 100% exempt from IHT, regardless of value. Unmarried partners pay 40% IHT on anything above £325,000 unless a Will directs assets elsewhere.
2. Transferable Nil‑Rate Bands — Up to £1,000,000
Unused £325,000 Nil Rate Band and £175,000 Residence Nil Rate Band transfer to the surviving spouse. This gives married couples a combined £1 million IHT allowance on second death.
3. Agricultural & Business Property Relief — Double the Protection
Each spouse can pass £2.5m of qualifying agricultural/business property IHT‑free. Marriage allows the unused relief on first death to transfer, giving £5m protection on second death.
4. Pension Death Benefits — Automatic for Spouses
Defined benefit schemes (NHS, Teachers, Civil Service, etc.) automatically pay 50%+ spouse’s pension to the surviving partner. Unmarried partners often do not qualify unless nominated and accepted by trustees.
5. ISA Inheritance Protection — Additional Permitted Subscription
When a spouse dies, the survivor receives an extra ISA allowance equal to the deceased’s ISA value, preserving tax‑free status. Unmarried partners do not receive this.
6. Capital Gains Tax (CGT) — No‑Gain/No‑Loss Transfers
Married couples can transfer assets between themselves tax‑free, enabling:
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use of two CGT allowances,
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selling assets in the name of the lower‑rate taxpayer,
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strategic tax‑efficient disposals. Unmarried partners pay CGT on transfers at market value.
7. Marriage Allowance — £252/year + Backdating
If one partner earns below £12,570 and the other is a basic‑rate taxpayer, 10% of the personal allowance (£1,260) can be transferred, saving £252/year. Can be backdated 4 years (worth up to £1,008).
8. Income‑Shifting Opportunities
By transferring income‑producing assets (shares, rental property, savings) to a lower‑rate spouse, couples can reduce household income tax significantly. This is not available to unmarried partners without the risk of capital gains tax on any transfer and using up IHT gifting allowances and Nil Rate Band for unmarried couples.
9. State Pension Inheritance (Old System)
For those with pre‑2016 pension entitlements:
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Married couples can inherit SERPS (up to 50–100%) and S2P (50%).
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Unmarried partners cannot inherit these entitlements.
10. Intestacy Protection — Automatic Rights
If you die without a Will:
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Your spouse automatically inherits under UK intestacy rules.
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Your unmarried partner inherits nothing, regardless of how long you lived together.
11. Home Ownership Security
If the home is in one partner’s sole name:
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A spouse has statutory rights to remain and inherit under intestacy.
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An unmarried partner may have no right to stay, no right to inherit, and may face eviction unless a Will or trust is in place.
12. Legal, Administrative & Financial Simplicity
Marriage simplifies:
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probate,
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pension nominations,
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death‑in‑service claims,
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hospital next‑of‑kin rights,
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tax planning,
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estate equalisation,
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long‑term care planning.
Unmarried partners must rely on complex workarounds: Wills, trusts, nominations, declarations of trust, cohabitation agreements — all of which can fail or be challenged.
Why this matters ...
Most couples assume “common‑law partner” status exists. It does not. The financial gap between married and unmarried couples is huge, especially at first death.
For many clients, the decision to marry is not romantic — it’s protective:
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safeguarding the home,
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preserving pension wealth,
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avoiding unnecessary IHT,
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ensuring the survivor is financially secure.
