The BBC has never and, if the philosophies of RTD and Moffat continue to hold sway, will never declare what is part of the DW "canon." This is okay.
The concept of "canon" within fan groups can be traced originally to Sherlock Holmes, but more relevantly to Star Trek. In fact, most of everything that modern fan groups do can be traced to Star Trek, including conventions, dressing up, "canon," and slash fiction. Doctor Who is not Star Trek, and should never pretend to be.
In most cases, the "canon" is what the creators of the show have decided are part of the official narrative. That's where Star Wars and Star Trek got theirs. Originally, it was George Lucas and Gene Roddenberry who decided what was official and what was not, though neither of them still do for obvious reasons. Star Wars actually has an official committee that decides it, the Lucasfilm Story Group.
The BBC has never come close to officially laying down a canon, saying what does and does not count. Originally, it was because no one had ever considered that that was a thing that they should even do. The next chance it had for that to happen was the '80s, which was largely characterized by the existence of an established fandom and an attempt to emulate cult science fiction shows instead of being the broad-audienced Saturday tea time show it had always been. But they didn't do it then either.
When RTD got the show restarted, he made a point to make sure that Big Finish continued to be able to make the Classic Doctor stories they had been making for five years at that point. He also, notably, never sat down and said what counted and what didn't. Moffat has been quoted that laying down a canon for Doctor Who would be impossible due to its subject matter.
DW simply doesn't have a canon, at least not one remotely comparable to the way you and so many other fans want to use that term. It does, due to its 50 years of existence in at least three forms (TV, comic, prose) and now the fourth since 1999 (audio) have something approaching a literary canon. This would be a list of all the greatest works within Doctor Who by which all other works are judged. And you'd be a fool if you said that all of DW's greatest stories are all confined to a single medium. Especially considering that there's more audio DW than there is televised That's 195 stories in the Main Range alone, not counting the Eighth Doctor Adventures, Fourth Doctor Adventures, Companion Chronicles, Gallifrey, free with DMW, free to Subscribers, Stage Plays, Lost Stories, Special Releases (including all of Dark Eyes,) or Early Adventures. To put that in perspective, the 200th Televised Doctor Who story was Planet of the Dead, during the 2009 year of specials. Simply add the EDAs plus Dark Eyes and you're almost to the end of Matt Smith. Add the Fourth Doctor Adventures and you've eclipsed it all. And that's still leaving out the Lost Stories (of which there are another 30 or so) and all the rest.