Do I need to register my copyright to sue for infringement?

Yes, for U.S. works. Although copyright attaches automatically when a work is fixed, 17 U.S.C. § 411(a) makes registration a precondition to an infringement suit, and Fourth Estate v. Wall-Street.com (2019) 586 U.S. 296 requires the Copyright Office to have acted on the application. Registering early also preserves statutory damages and attorney fees under section 412.

Yes: for U.S. works, registration (not just application) must be in hand before filing suit. Copyright protection itself attaches automatically the moment an original work is fixed in tangible form (17 U.S.C. § 102); no notice or registration is needed to own the rights. But 17 U.S.C. § 411(a) makes registration a precondition to an infringement action, and the Supreme Court held in Fourth Estate v. Wall-Street.com (2019) 586 U.S. 296 that the Copyright Office must have actually acted on the application, expedited "special handling" exists for litigation deadlines, at a premium fee. Timing controls remedies too: under 17 U.S.C. § 412, statutory damages (up to $150,000 per work for willful infringement) and attorney fees are available only if the work was registered before the infringement began or within three months of first publication. Registering promptly is therefore cheap insurance. For claims up to $30,000, the Copyright Claims Board offers a small-claims alternative to federal court. Infringement claims run three years (17 U.S.C. § 507(b)).

Authority: 17 U.S.C. § 411; Fourth Estate v. Wall-Street.com (2019) 586 U.S. 296