fathom - 3:54 am on Apr 3, 2012 (gmt 0)
While you have a commonlaw copyright the moment you put a work into a tangible form that only allows you to pound your chest and yell "I'll sue"... you cannot actually sue anyone for damages without first proving you own a copyright.
Under Section Registration and civil infringement actions 411.(b)(1) of the copyright law states "A certificate of registration satisfies this requirement" (for proof of copyright).
Just saying you own copyright will never get you into a court of law let alone filing for court action... you need to submit your issuance number as part of your claim.
Quoting The Copyright Office Circulation 01 page 7 [copyright.gov...]
In general, copyright registration is a legal formality intended to make a public record of the basic facts of a particular copyright. However, registration is not a condition of copyright protection. Even though registration is not a requirement for protection, the copyright law provides several inducements or advantages to encourage copyright owners to make registration.
Among these advantages are the following:
• Registration establishes a public record of the copyright claim. Registration may be made at any time within the life of the copyright. Unlike the law before 1978, when a work has been registered in unpublished form, it is not necessary to make another registration when the work becomes published, although the copyright owner may register the published edition, if desired.
• Before an infringement suit may be filed in court, registration is necessary for works of U. S. origin.
• If made before or within five years of publication, registration will establish prima facie evidence in court of the validity of the copyright and of the facts stated in the certificate.
• If registration is made within three months after publication of the work or prior to an infringement of the work, statutory damages and attorney’s fees will be available to the copyright owner in court actions. Otherwise, only an award of actual damages and profits is available to the copyright owner.
• Registration allows the owner of the copyright to record the registration with the U. S. Customs Service for protection against the importation of infringing copies. For additional information, go to the U. S. Customs and Border Protection website at www.cbp.gov/.