No, there isn’t a specific duplicate content penalty. There are different kinds of a Google penalties, but a so-called duplicate content penalty does not exist. Internal duplicate content can have an effect on how a website appears in the search results, but it does not lead to a penalty.
Google has a part in their Webmaster Guidelines that warns against the wilful creation of duplicate content, as this may be penalised through various algorithms and filter, such as the Google Panda update.
Duplicate content on a site is not grounds for action on that site unless it appears that the intent of the duplicate content is to be deceptive and manipulate search engine results. If your site suffers from duplicate content issues, and you don’t follow the advice listed above, we do a good job of choosing a version of the content to show in our search results.– Google Guidelines for Webmasters
So there is no need to worry about “accidental” duplicate content?
Google tries to filter out duplicate content to show users as few redundant results as possible. This already works quite well in most cases, but every webmaster should nevertheless avoid duplicated content on their websites.
Are there different kinds of duplicate content?
Yes. There is internal as well as external duplicate content, “DC” in short.
Internal duplicate content will already occur if the same content on a website can be accessed through multiple URLs.
External duplicate content may occur when a website is available in multiple language versions and these different versions appear in the search results for the same search market (for example google.co.uk).
Checking your own website for duplicate content
The SISTRIX Optimizer performs an automatic on-page evaluation of your website and will show you all relevant SEO errors. This analysis is complemented by explanations of every error type and concrete guidelines on how to improve your OnPage optimisation. Duplicate content-errors (Duplicate Content Found) are comprehensively displayed for each separate URL.
Is duplicate content SPAM?
Matt Cutts, head of Google’s webspam-team, once again makes it clear that duplicate content is not considered spam, which would be punished. Although, if someone was to excessively gather content (by automated means for example), without creating added value for users, they might actually get in trouble.
Video-explanation from Matt Cutts / Google on this subject
How does Google handle duplicate content?
How does Google handle duplicate content and what negative effects can it have on rankings from an SEO perspective?