There are a number of different factors that determine whether or not a childcare provider is required to be registered with Ofsted. A certificate of registration should be on display at the childcare setting when you visit.
Ofsted carries out inspections to check the quality of the care provided. They then produce inspection reports detailing their findings. You can use these reports to help you decide which providers to visit, to confirm what you found as a result of the visit, or as a result of a recommendation by someone else. Inspection reports give you information about what the inspector found on the day of the inspection.
All reports include grades on the quality of provision and things the childcare provider can do to improve. When you visit, you can check what the provider has done. It is also important to check the date of the last Ofsted inspection as it is possible that things may have changed.
Information on Ofsted registered childcare, including inspection reports can be found on the Ofsted website - Find an inspection report.