Nannies at present are not required by law to hold any childcare qualifications.
However if they wish to become part of the Voluntary Ofsted Childcare Register (OCR) they have the same requirements as a childminder, the only difference being is that they are caring for the children in their own home.
To register, a nanny needs to complete online application via the Government Gateway website.
https://online.ofsted.gov.uk/OnlineOfsted
It will cost around £103 and needs renewing every 3 years.
As a nanny you will also need a Paediatric First Aid certificate, The Common Cores Skills and Knowledge in Childcare, Enhanced DBS Check and Public Liability Insurance.