... of a claim is not the same thing as receiving a copyright. For example, you might submit a manuscript to the LOC which is in the public domain. Before you can receive the copyright, that claim has to be researched for its originality. If you had submitted, say, the text of
Pride and Prejudice under another title and your name, you would not be entitled to the exclusivity of a copyright; the LOC would have to research the authenticity and originality of your text before issuing a legally-binding copyright to you.
Registration of claim is a protection against other claims while that research is being done, if research is required. If the process isn't completed within five years, you don't have as much standing in court if you expect relief for someone using your work. In the same way, you can simply put a copyright symbol ( (c) ) on your work and it will retain some protection, but only for a limited time. If you fail to complete the copyright process within five years, the courts will often determine that you had no interest in either pursuing or defending that copyright.
Here's the text of how that goes. The important consideration is "after examination":
(a) When, after examination, the Register of Copyrights determines that, in accordance with the provisions of this title, the material deposited constitutes copyrightable subject matter and that the other legal and formal requirements of this title have been met, the Register shall register the claim and issue to the applicant a certificate of registration under the seal of the Copyright Office. The certificate shall contain the information given in the application, together with the number and effective date of the registration.
(b) In any case in which the Register of Copyrights determines that, in accordance with the provisions of this title, the material deposited does not constitute copyrightable subject matter or that the claim is invalid for any other reason, the Register shall refuse registration and shall notify the applicant in writing of the reasons for such refusal.
(c) In any judicial proceedings the certificate of a registration made before or within five years after first publication of the work shall constitute prima facie evidence of the validity of the copyright and of the facts stated in the certificate. The evidentiary weight to be accorded the certificate of a registration made thereafter shall be within the discretion of the court.
(d) The effective date of a copyright registration is the day on which an application, deposit, and fee, which are later determined by the Register of Copyrights or by a court of competent jurisdiction to be acceptable for registration, have all been received in the Copyright Office.
Now, if the copyright office issued notification of copyright--with the office's seal--then, that's valid in court. If you were able to do that with the simple registration fee, that's great. Most works anticipating commercial publication require more research, for which the LOC charges additional hourly fees. (On edit, I should add that commercial enterprises get kind of a pass on the latter issue, especially for ongoing publications--the LOC assumes they're editorially vetting their own material--that's why newspapers and magazines get lump sum annual rates for copyrighting their own material. For individual authors not associated with an established firm, it's another matter.)
Cheers.