"Valid" isn't the right question, the right question, is does the plaintiff's compaint state a cause of action? The judge doesn't know you do business as an LLC, all they know are the facts alleged in the complaint, and all a demurrer does is eductae the plaintoff about what they've done wrong so they can fix it.
Generally, you won't escape this lawsuit because plaintiff got your form of business wrong. INstead of demurrer, just answer the complaint on behalf of "ABC LLC, wrongly sued as John Doe DBA ABC," which will save time.
Since you have a claim against plaintiff, you'll also want to file your cross-complaint at the same time you file your answer and make yourself a cross-complainant and them a cross-defendant.
Avvo doesn't pay us for these responses, and I'm not your lawyer just because I answer this question or respond to any follow-up comments. If you want to hire me, please contact me. Otherwise, please don't expect a further response. We need an actual written agreement to form an attorney-client relationship. I'm only licensed in CA and you shouldn't rely on this answer, since each state has different laws, each situation is fact specific, and it's impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue.
Without more information and without seeing the allegations of the complaint, no one can really say for sure. However, if the complaint alleges that the plaintiff had a contract with you personally and d/b/a a business name, the cause of action would be valid if it otherwise alleges all of the essential elements for breach of contract. It is plaintiff's burden to prove the existence of the contract with you individually and d/b/a the business name.
In order to sue for breach of contract, the plaintiff's complaint must allege facts sufficient to constitute a cause of action. Normally, the contract must either be attached to the complaint or set forth verbatim in the body of the complaint. (Otworth v. Southern Pacific Transportation Company (1985) 166 Cal.App.3d 452, 459; Twaite v. Allstate Insurance Company (1989) 216 Cal.App.3d 239, 252.) Such needs to be attached or set forth verbatim because, as noted in Stoddard v. Treadwell (1864) 26 Cal. 294, 303:
"A contract may be declared on according to its legal effect or in haec verba. If the former mode should be adopted, then the defendant may by the rule of the common law in a proper case crave oyer [i.e. hearing] of the instrument, and if it appear that its provisions have been misstated, he might set out the contract in haec verba and demur on the ground of the variance. But where a plaintiff himself sets forth the contract in the terms in which it is written, and then proceeds by averment to put a false construction upon the terms, the allegations, as repugnant to the terms, should be regarded as surplusage, to be struck out on motion. Utile per inutile non vitiatur. (1 Ch. Pl. 232.) [“What is useful is not vitiated by the useless”]"
Contract terms may be alleged generally according to legal intendment. (Construction Protective Services, Inc. v. TIG Specialty Ins. Co. (2002) 29 Cal.4th 189, 198-199.) Pleading contracts by legal effects involves alleging the relevant terms in substance. (McKell v. Washington Mutual, Inc. (2006) 142 Cal.App.4th 1457, 1489.)
For breach of oral contract, as 4 Witkin, Cal. Proc. 4th (1997) Plead, § 483, p. 575, notes:
"If oral, the exact words used can seldom be correctly alleged, and are evidentiary in nature. Hence, the oral contract is pleaded according to its legal effect. (See, for complaints held sufficient, Poly, Heilbron & Co. v. Williams (1894) 101 C. 648, 36 P. 102; Christensen v. Cram (1909) 156 C. 633, 105 P. 950 [inferential pleading of executed contract of sale (plaintiff "sold" property for certain price) held sufficient in absence of demurrer]; Weitzenkorn v. Lesser (1953) 40 C.2d 778, 780, 256 P.2d 947; Crawford v. Duncan (1923) 61 C.A. 647, 215 P. 573; Holstrom v. Mullen (1927) 84 C.A. 1, 257 P. 545; Hillman v. Hillman Land Co. (1947) 81 C.A.2d 174, 177, 183 P.2d 730; Merlino v. West Coast Macaroni Mfg. Co. (1949) 90 C.A.2d 106, 109, 111, 202 P.2d 748; Roberts v. Wachter (1951) 104 C.A.2d 281, 231 P.2d 540; and see Cal. Civil Practice, 3 Business Litigation, §24:104; 7A Am.Jur. P.P. Forms (1995 ed.), Contracts, §71.)"
Therefore, one would have to review the actual complaint to see if you can demurrer to the breach of contract cause of action. If the complaint alleges sufficient facts to constitute a breach of contract cause of action, your demurrer would be overruled, and you would have to file a motion for summary judgment. Only a motion for summary judgment will consider the evidence. A demurrer only evaluates the allegations of the complaint without extrinsic evidence.
Frank W. Chen has been licensed to practice law in California since 1988. The information presented here is general in nature and is not intended, nor should be construed, as legal advice for a particular case. This posting does not create any attorney-client relationship with the author. For specific advice about your particular situation, consult with your own attorney.