What is the difference between marriage and civil partnership?
In England and Wales the two are now legally almost identical, and the differences that remain are largely historical, symbolic and procedural rather than substantive.
The background. Civil partnerships were introduced in 2004 for same-sex couples, at a time when marriage was unavailable to them. Same-sex marriage followed in 2013. That left an asymmetry — same-sex couples could choose either, opposite-sex couples only marriage.
That was successfully challenged in the Supreme Court in Steinfeld and Keidan (2018), and civil partnerships were opened to opposite-sex couples in 2019. Both are now available to all couples.
Where they are the same:
Legal rights and obligations are effectively equivalent — inheritance, next of kin, parental responsibility, pensions, immigration, and property rights.
Tax treatment, including inheritance tax exemption between partners and the marriage allowance, which applies to both.
Financial provision on dissolution follows the same principles as divorce.
The remaining differences:
Formation. A marriage is created by spoken declarations before witnesses. A civil partnership is created by signing the register, with no words legally required — though many couples add a ceremony.
Religious element. Marriage may be religious or civil. Civil partnerships are civil, though religious premises may be approved for registration in some circumstances without religious content.
Terminology. Marriages end in divorce; civil partnerships are dissolved. Partners are civil partners, not spouses, though the legal effect is the same.
Adultery is a concept in marriage law and not in civil partnership law — largely moot in England and Wales since no-fault divorce was introduced in 2022.
International recognition is the most practically significant difference. Marriage is recognised near-universally; civil partnerships may not be recognised abroad, or may be treated differently, which matters for couples who travel, work or own property overseas.
Conversion between the two is possible in some circumstances.
Cohabitation confers neither — there is no common-law marriage.