As a domiciliary care service (home care service) you only need to register with the Care Quality Commission (CQC) if you are offering the regulated activity of 'personal care'. 

Personal care is where you are providing help and assistance with tasks of a personal nature such as washing and bathing, applying creams or lotions, toileting, oral hygiene, physical eating and drinking assistance, help in changing continence pads, dressing and getting ready for bed, applying makeup and hair care.

You must register with the CQC if providing these services. Not registering and carrying on a service that falls into this bracket is against the law. 

If you are not offering personal care e.g. just assisting with general household help such as cleaning around the house, helping with shopping or providing companionship to clients, then you do not need to register. 

By the time families start looking at care options, it's often quite far down the road and when day to day tasks become more difficult, and as such, most clients will need some level of assistance with personal care. A lesser number of prospective clients are solely looking for household help and can take care of their personal care completely independently - as more often than not this general day to day support can be picked up by friends and family.