When a document is registered for a building society, it can happen in two ways. You can think of it like this:

1. The document becomes part of the register itself. This means the actual document is added to the official records.

2. Instead of the whole document, some important details about it are put into an electronic register. This is like writing down the main points of the document in a computer system.

Either of these ways counts as registering the document. This is how the government keeps track of important information about building societies.