Every employer in the UK has a Staging Date.  This date is the date by which the Employer must already be compliant with the new auto-enrolment rules.

Click here to find out your personal staging date
It is important to note that:
An employer can start an auto-enrolment scheme prior to its staging date, but not after its staging date.
These dates in the table below apply to when an Employer must start to comply with the new regulations in respect of auto-enrolment.  As stated above, the date cannot be delayed, but can be voluntarily brought forward.
In October 2012, each Employer had a date dependent upon the number of workers employed. The table below sets out the revised automatic enrolment dates for all employer sizes.
Employer size (by PAYE scheme size) or other description Automatic Enrolment duty date
Employers without PAYE schemes 1 April 2017
New employers Apr 2012 to Mar 2013 1 May 2017
New employers Apr 2013 to Mar 2014 1 July 2017
New employers Apr 2014 to Mar 2015 1 August 2017
New employers Apr 2015 to Dec 2015 1 October 2017
New employers Jan 2016 to Sep 2016 1 November 2017
New employers Oct 2016 to Jun 2017 1 January 2018
New employers Jul 2017 to Sep 2017 1 February 2018
New employers Oct 2017 Immediate duty