I think we need a little more information to answer your question. Is this on a child support order that is being enforced by the county child support services division or one that your husband is enforcing himsel in the regular family law court?
From your question, I gather that you are the support obligor who is in arrears - is that correct?
If you motion to determine arrears is going to include a response to your ex-husband's declaration then you should provide your own declaration regarding the relevant facts. You will probably need to prepare an FL-300 form (request for orders) and a FL-490 form (application to determine arrearages).
Without knowing more about your situation and seeing your documents, it's hard to be more specific.
Good Luck!! I'm glad to help if I can. No charge for your first consulation.
The answer to your question is not intended to provide you with legal advice you should rely on, only a general indication of what the law might provide. You may have provided only a limited description of your situation and I may be unaware of important facts that could affect your case. My answering your question does not create an attorney-client relationship between us.
Sounds like you haven't actually filed the motion yet to determine arrears. What is the supplemental declaration in response to? Is there another motion pending other than the one you were ordered to file? What was your ex husband "supplementing" i.e. what document or motion or opposition/response? You can address your response to that "supplemental declaration" in your motion to determine the arrears. You haven't really provided enough information in your question to enable a more meaningful or helpful response.
Based on what you have stated, it sounds like you went to Court, to try and collect on child support that has never been paid to you in 12 years. It sounds like your paperwork was not specific enough for the Judge to make an order.
I believe you need to provide points and authorities as to why he should be ordered to pay you after all this time. Sounds like you need a specific accounting, i.e., court order, date that support was due, how much if anything was paid, break down to include each and every month from the time the order was made, along with accrued interest. I believe that is what you are suppose to do, either in a New Motion, or a Supplement to your current motion (if the Judge set a return date.)
I am in Los Angeles, and conduct low cost clinics on Fridays & weekends, and can assist you in document preparation or full representation.
Please note that this answer does not constitute legal advice, and should not be relied on, as each situation is fact specific, and it is not possible to evaluate a legal problem without a comprehensive consultation and review of all the facts and court pleadings filed in the case. This answer does not create an attorney-client relationship