Change your name in two main ways
There are two main ways of changing your name officially; these are by Deed Poll and by Statutory Declaration.

A Statutory Declaration is a legal document which is signed in the presence of a Solicitor, Commission of Oaths, Notary Public or Justice of the Peace. Once signed, the change of name will be effective and from that date you will be known by the name you have chosen. You should retain the original Statutory Declaration and in the event of being required to provide evidence of the change, provide a certified copy. This may be required when applying for a passport, driving license or opening/changing bank account.
A Deed Poll is an alternative legal document. It is not necessary to sign a Deed Poll before someone acting in an official capacity; however it must be signed in the presence of two witnesses providing they are not relatives. Once signed it is possible to register a Deed Poll within the Royal Courts of Justice, although this is not essential. Once registered a notice is published in the Gazette newspaper and the Deed Poll document is then stamped and returned. Change of name by Deed Poll can sometimes be required if a person is a member of a particular institute or professional organisation.
For many the preferred option is to have a Statutory Declaration because it is signed in the presence of an officially recognised person and receives an official stamp. Also, except for the fee for preparing the Statutory Declaration and a small (£5.00) charge when the document is signed, there are no other fees payable, whereas if you change your name by Deed Poll and choose to register it, there are fees payable in addition to the fee for preparing the document.
A child under the age of 16 can only change their name acting through someone who has Parental Responsibility for them and with the consent of everyone who has Parental Responsibility for them.
Parental Responsibility is a legal term that means having all the legal right, duties, powers and responsibilities for a child.
Having Parental Responsibility for a child means you are responsible for, and have the right to be consulted about, the child’s health, education, religion and welfare.
If the other parent with Parental Responsibility will not consent you should consider applying to your local family court for permission to change your child’s name.
There are few circumstances where you can change the name on your child’s birth certificate.
You do not need either a Deed Poll or Statutory Declaration if you want to take your spouse’s/partner’s surname. It is sufficient to send a copy of your marriage certificate or civil partnership certificate together with a covering letter and your records and documents will be changed.
If you wish to have a double-barrel surname then you will need a Deed Poll or a Statutory Declaration.
It may be possible to return to your original name by presenting your marriage certificate and your decree absolute, or in the event of a civil partnership, your civil partnership certificate and your final order, however some organisations will require either a Deed Poll or Statutory Declaration.