You need to carefully read the marital dissolution agreement and the three (3) reconciliation period for the reimbursement of expenses to see if there is a stated deadline to submit expenses for reimbursement and if not done so by a certain time period that such are waived. If such is not stated in the document then under the laws of all states the time period to submit such essentially is a reasonable time period.What is reasonable depends upon the facts of each matter. If the three (3) month time period is not set in stone per the agreement that you have written about then you probably will have to reimburse the "ex" the amount despite the submission being very late.