If you employ the carer you need to comply; and if you and others employ the carer you are each responsible based on the earnings you each pay them. If the carer works for an agency or their own limited company that agency/company are responsible for complying with auto-enrolment duties.
If they’re self-employed there are criteria to decide whether duties still apply. Does the carer:
- have control of the hours they work?
- have their own public liability insurance?
- provide care services for other people?
- register themselves as self-employed with HMRC?
- not get paid when on holiday or unable to work due to sickness?
If most or all of the above are true, it would be reasonable to consider that they’re undertaking the work as part of their own business. If they’re undertaking the work as part of their own business, they can be considered ‘truly self-employed’ and aren’t subject to auto-enrolment.