As well as introducing the requirement to give details of Persons with Significant Control (“PSCs”), the UK Small Business Enterprise and Employment Act 2015 has replaced the manner in which key details of companies and limited liability partnerships are updated.
From 30 June 2016, annual returns for UK companies (and limited liability partnerships) have been replaced with confirmation statements, although they will serve a similar purpose to that of annual returns.

At least one confirmation statement – Form CS01 or LLCS01 - must be filed each year, however, unlike the annual return there will be no set date when a confirmation statement must be filed. Effectively, no more than 12 months must elapse between each confirmation statement being filed. 

For a detailed explanation please see the guidance issued by Companies House

The first confirmation statement must not be more than 12 months after the date of the last annual return and must also give details of any PSCs.

It’s a criminal offence not to file a confirmation statement within 14 days of the end of the relevant review period. If you don’t do this, the company and its officers are open to prosecution.