Once you have chosen your pension scheme your obligations are as follows:
Assess the workforce
If earnings are over £10k, and they are 22+ and below retirement age are 'eligible workers', which means they have to be automatically enrolled.
If an employee earns up to £10k, they are 22+ they can ask to be enrolled onto the scheme.
Contribute and communicate the scheme to your employees
You have to set the employee/ employer contribution rates which will be paid over to the pension, the minimum rates are 1% for the employee and 1% for the employer so at a minimum, 2% is reported over to your pension scheme monthly
You have to explain the impact of this to your employees and what it means to them, and also give them the right to opt out
Enroll your staff and set up pension scheme
All the enrolment set up data should be set up, pension contributions configured and processing of any opts out that you receive.
You will be required to supply details of new enrolment, leavers/changes and contributions to your pension provider in a specific format so that contributions can be made.
Practically, all the above can be outsourced to us - we normally have a setup fee of £300 +VAT and a minimum fee of £25-35pm for a block of up to 5 people then £5+VAT per employee thereafter in order to carry out this work.