When a limited company is incorporated, Companies House assumes that the registered office address of the private company is the place where company records are kept, and is also the place where those records can be made available for public inspection.
However, for a variety of reasons it may be necessary to register something called a Single Alternative Inspection Location (SAIL) address. This is often because a company might be run from home, and the business owner is reluctant to have their home address listed on a public directory.
The SAIL address is often the office of the company's accountant but can be any other address. Registering or changing a SAIL address, however, can be complicated. Different forms must be used, according to your precise circumstances, and this can be frustrating to deal with when you just want to get on with running your company.