When you file a lawsuit in DC against a DC corporation you have to serve the corporation or one of its officers.  You can do it by US Mail, Certified, Return Receipt Requested.  But if an unauthorized person signs for the letter with the legal documents, you have a problem: There is caselaw which specifically holds that, especially against the D.C. Government, notice of a lawsuit is improperly served unless the exact, specifically authorized person, signs.  I’ve known cases to be thrown out of court for this reason.  So what I do is *serve* by certified mail containing D.C. Form 4 (the Waiver of Service form).    If Form 4 and accompanying papers are used, you must wait 60 days (90 if the D.C. Gov’t).  If you don’t use Form 4, you need pay the money and use a process server.  Why use Form 4?  I always use the Waiver of Service Form & send it certified. Then they are liable for the costs of service if they don’t respond.