What is an annual return?

Every year a company is required to make an annual return to Companies House. This is a form setting out the registered details of the company: its name, number, registered office address, business activities, details of directors, secretary and shareholders, etc. The form will be sent out by Companies House and must be signed and returned with the filing fee, which is £30 if done on paper and £15 if done by electronic filing.
The purposes of the annual return are:
(1) to keep the information about the company on the official register up to dat:
(2) it makes searching the information at Companies House much easier - it is only necessary to look for changes since the last annual return:
(3) the shareholders' details are only registered on an annual basis (in listed companies they are changing daily)
(4) the revenue from the annual returns is an important part of the Companies House's income, paying for the regsitration costs of maintaining the register.