When can notice affect damages?
Where section 287(a) applies and marking is deficient, damages generally begin only after actual notice of infringement. Lubby Holdings v. Chung distinguishes identifying the patent from identifying the activity believed to infringe, accompanied by a proposal to stop it through a license or otherwise. Filing an infringement action itself constitutes notice under the statute.
Can a letter lead to a suit by the recipient?
It can contribute to an actual controversy supporting declaratory relief. Under MedImmune v. Genentech, the court examines all the circumstances. Do not assume that calling a letter an invitation to talk eliminates the legal significance of its specific accusations.
How should I choose between a letter and a complaint?
Assess the evidence, desired business outcome, relevant deadlines, and possible response with counsel. A letter and a complaint serve different purposes. If filing is the chosen route, Rule 11 requires a reasonable inquiry supporting the court filing; sending an earlier letter does not replace that work.