Do I Need Canonicalization?

[atakala]

Hey moz fans,
I have a site and when I run through with site seo audit tool, they always give me a error that none of your page has canonical tag.
So my question do I need canonical tag ? 
I'm asking because I think I don't have any duplicate web pages.
Even though I dont have duplicate pages, is it still necessary to have canonical tag in the original pages? 
And also I want to know how do you guyz know , whether your site has duplicate pages?
Thank you.

[BCutrer]

It's always a good practice. It also depends if you are using a CMS that has an automatic 301 for the WWW vs the non for the site. For simple sites that's the only real reason that you would need it. I still like to have the tag, the major search engines have been recommending it and I usually do whatever makes Google happy if I can.

You can see if you have duplicate content if you subscribe to Moz in their campaign tools. If not there are a few free tools that will allow you to as well.