You asked a tough question for which there are several competing answers, depending on who you ask. But since you’re asking me, I typically advise: No, the LLC or corporation  cannot act as such before its state registration (for a corporation, its Articles of Incorporation; for an LLC its Articles of Organization is filed. If it does do business prior to filing, any claims against the corporation or LLC will be the responsibility of its owner(s), since the liability shield created on formation didn’t exist. That said, if you want to engage in contracts using the corporate or LLC moniker, you could execute the subject agreement by saying (for example) “Main Street LLC, a California limited liability company in formation”. This doesn’t give you the limited liability otherwise offered by having a corporation or LLC, but it does let the other side know that it will ultimately be the corporation or LLC that is the party to the contract, not you individually.