Family

The Family tools take one household's situation and set out what the law says about it, step by step and with the official source named. The first is the baby surname checker: type both parents' surnames, say whether they are married and who registers, and it lists the surnames that come from those names.

• England and Wales, Scotland and Northern Ireland each have their own registration rules, so the checker asks where the birth is registered.
• Each result names the deadline, who may register, what happens when the parents disagree and how a later change of surname works.
• The surnames you type stay in your browser. Only the family situation goes into a shared link.

Unlike most of Europe, the UK has no rule that hands a child a particular surname. The register records the surname by which the child is to be known, and whoever registers the birth gives it. That can be the mother's surname, the father's, both joined in either order, or a different name altogether.

Marriage matters for a different reason: it decides who may register. Married parents and civil partners can each register alone. When the parents are not married, the father is entered only if both register together or a declaration or court order allows it. Registration also gives an unmarried father parental responsibility, for births registered in England or Wales from 1 December 2003.

Brothers and sisters need not share a surname, since each registration is a separate choice. When parents cannot agree, a court decides on the child's welfare. A later change needs everyone with parental responsibility to agree, or a court order.

The surname is written into the register when the birth is registered. That must happen within 42 days in England and Wales, 42 days in Northern Ireland and 21 days in Scotland, with a local registrar. The birth certificate then shows the name.

Changing it afterwards is harder than choosing it. In England and Wales a deed poll is the usual route, and from 16 the child must agree. Scotland records one change of surname while the child is under 16, and Northern Ireland one while the child is under 18.

These pages explain what the law and the official guidance say, with each source named. They do not give advice on which surname to choose or how to settle a family disagreement; for that, a solicitor or the register office can help with a specific case.