In California, the deadline you have to serve your Defendant's Claim (Form SC-120) depends on when you were served with the Plaintiff's Claim (Form SC-100):
If you received a copy of the Plaintiff's Claim more than 10 days before the trial date, you have to serve the plaintiff at least 5 days before the hearing.
If you received a copy of the Plaintiff's Claim 10 days or less before the trial date, you have to serve the plaintiff at least 1 day before the hearing.
If the service of the Defendant's Claim is improper or untimely, the judge can either postpone the small claims trial, or proceed with the trial if the Plaintiff does not object. The judge will not likely just dismiss the Defendant's Claim. That is not reason enough.
The information presented here is general in nature and is not intended, nor should be construed, as legal advice. This posting does not create any attorney-client relationship with the author (who is only admitted to practice law in the State of California). For specific advice about your particular situation, consult your own attorney.
No he did not miss a deadline. You can ask the court for more time when you go to trial. Or if you are ready, you can go to trial and have the Judge hear both sides of the issues at the same time - your complaint against him and his counter-claim against you.
This is general legal information, not intended to apply to your specific case. And I may not be licensed to practice in your particular state. Under Federal Law, I am a debt relief agent.
As usually, Mr. Chen has given very good advice.
The general advice above does not constitute an attorney-client relationship: you haven't hired me or my firm or given me confidential information by posting on this public forum, and my answer on this public forum does not constitute attorney-client advice