Box 9b Birth date
Boxes 9, 9a, 9b, 9c, and 9d contain information related to secondary insurance coverage if it exists.
Box 9b contains the date of birth of the carrier of the secondary policy under which the client is covered. If the client is not the carrier of their own secondary policy, then they are most likely the covered by the secondary policy held by their spouse, parent, or significant other. This information is entered at the bottom of the Client Insurance Information.