A IV-D case number is a 9-digit number that usually begins with the number 9. A docket number contains 10-digits and begins with the year (like 2016). If the docket number you have looks like this: 16-001234-DM or 16-1234-DM then you must omit the dashes and alpha characters when entering the number on the website. Your entry must be all numeric digits, contain 10-digits and entered in the following manner: 2016001234.
Check any mail you have received from a Child Support Specialist or your Friend of the Court. The IV-D number may be found at the bottom of the letter. (See sample below)