SoI'm filling out forms for After-school Care for DD1 and it says I need her CRN as well as my CRN for the CCR, how do I find out what it is?

THe school scretary said it should be on any letter I have from Centrelink, but I only get FTA&B so not sure if it would come up on those letters or not.

Should I go into CL and ask for it?