**Yes, definitely.**

What follows is not an exhaustive list, but should give you some idea of the sort of discrepancies and mistakes that exist.

* The most significant example comes from *Goblet of Fire*. In an early printing of the book, in the scene where Voldemort’s victims emerge from his wand, James came out before Lily, despite Lily having been killed more recently. This was revised in later printings.

  See the question http://scifi.stackexchange.com/q/2649/3567 for more details.

* @DVK asked a question about six months ago about discrepancies between the main seven books, and the supplementary books *Fantastic Beasts and Where to Find Them*, *Quidditch through the Ages* and *The Tales of Beedle the Bard*.

  My answer to http://scifi.stackexchange.com/q/46092/3567 contains a list of the slip-ups that I know about.

* Pottermore has also thrown up some discrepancies between the books, and the “word of God” additional text and interviews by JK Rowling. See @Slytherincess’s Meta question http://meta.scifi.stackexchange.com/q/3568/3567 which highlights one such example.

* The Harry Potter Wiki isn’t generally considered canonical or accurate on this site, but their list of [mistakes in the Harry Potter books](http://harrypotter.wikia.com/wiki/Mistakes_in_the_Harry_Potter_books) is probably the closest to an exhaustive list that you’ll find. (Asking for the complete list on this site would almost certainly be closed as “too broad”.)

* A running joke on this site is that the numbers in the series are inconsistent. 

  For example, Nearly Headless Nick’s birthday in *Chamber of Secrets* is the event which helps set the books in the 1990s, but then weekdays don’t match up with their dates. We also have people whose ages are inconsistent from book to book, or how small the Hogwarts intake seems to be, despite the size of the castle, and so on. Searching this site is bound to find you some examples.

  From [another FAQ page](http://web.archive.org/web/20041009205903/http://www.jkrowling.com/textonly/faq_view.cfm?id=63), addressing one particular dating mistake:

  > Maths is not my strong suit (though it's better than my geography, as those who have found the most recent Easter Eggs might already know).
* JK Rowling has acknowledged, on multiple occasions, that there are mistakes in the books. From an [FAQ page on her website](http://web.archive.org/web/20110607110538/http://www.jkrowling.com/textonly/en/faq_view.cfm?id=108):

  > **How do you remember everything from different books when you are still writing the HP series?**

  > As obsessive fans will tell you, I do slip up! Several classrooms move floors mysteriously between books and these are the least serious continuity errors! Most of the fansites will point you in the direction of my mistakes. But the essentials remain consistent from book to book because the story has been plotted for a long time and it is clear in my mind.