Of the major sources of information by which the list is updated regularly, meaning once a month, once every three months or every six months, income tax is number one. We no longer add to the list: there are updates and address changes. There is a problem on the income tax side. We refer to this elsewhere.
As for drivers' licences, we have agreements with most of the provinces, but not with Quebec. In fact, in this case, the Chief Electoral Officer provides information directly to the list. He gets this information from similar sources. Finally, the civil registry is used to purge the names of deceased individuals from the list.
There are other agreements. For example, Citizenship and Immigration Canada provides us with the list of new citizens. Over 90 per cent of them agree to have their name added to the voters' list. It's possible to do so once people become Canadian citizens, but not before.
In short, these are the main sources of information used to periodically update the voters' list.