Legal Question in Business Law in California

You are the plaintiff. I assume you lost. You have no right to appeal. Your right to vacate the judgment is dependent upon your having failed to appear at the hearing, not on the court having made a mistake of law. Were you at the hearing? Look up and read Code of Civil Procedure sections 116.710 through about 116.795.

What does the defendant's response say? That might be instructive.

116.730 might shed some light on reply briefs, at least indirectly. However, it kinda looks like you are trying to "back door" an appeal when you have no right of appeal.

I have to retract my previous answer. A defendant OR plaintiff who gets a defective judgment (containing a clerical error OR applying "an incorrect or erroneous legal basis for the decision") in Small Claims can move to have it vacated under Code of Civil Procedure section 116.725(a)(2).

So, that still leaves the question unanswered as to whether the parties may file an opposition and then a reply, just as can be done when a motion is filed in Superior Court, and if so, when must the opposition and the reply to the opposition be filed and served.

I think the answer is found in the context of Judicial Council Form SC-108, the Request to Correct or Cancel Judgment and Answer. The design of, and instructions for, use of the form clearly indicate the intent of the rule-making body (the Judicial Council) that there be a request, an answer, and a hearing. This seems to preclude a reply brief by the requesting party. See also Rules of Court section 3.2107(b) and its use of the permissive "may" in the context of the court holding a hearing.

Note also CCP sections 116.920 giving the Judicial Council rulemaking authority, and 116.930 requiring or permitting the preparation and distribution of small-claims procedures manuals for use by judges or the public. If your court has such a public-use manual per 116.930(b), try to get a copy.

Another possible line of reasoning on this topic is to start with CCP 116.130(h), the small-claims definition of a motion, then move to 116.140(a) which says that a certain portion of CCP 1005(b) doesn't apply. This would, under the legal maxim "exclusio unius inclusio alterius" (the exclusion of one thing implies the inclusion of the other" mean that the provisions of CCP 1005(b) for the filing opposition and reply papers, and the timing, would apply, and I invite you to look at this provision. However, I still think the implication of SC-108 and Court Rule 3.2107(b) prevail.

If you have important arguments to make, make them at the hearing. An alternative might be to file and serve reply papers anyway; the worst that's likely to happen is that the judge will disregard them.