How to print custom field on sales Invoice via subscription (from subscription plan table)?

Hi all,
I Need one costume field on sales invoice print,
Step I am following,

  1. Created one costume field in “Subscription plan detail” from doctype, name is (discriptionss)
  2. create subscription plan & select plan
  3. In that plan I have entered, (qty,plan,descriptionss,Item name)
    4)After saving Subscription plan, A sales invoice created Automatically
    5)the costume field “discriptionss” should be print on sales invoice.

How I can achieve this???
Thanks in advance

You will have to create a new custom field in sales invoice called “Descriptions” (or any other name of your choice) and make it a data field. Then in fetch from box, type the following:

where xyz = name of the doctype of the child table “Plans” and,
abc = name of the descriptions field in plans doctype.

Hope this helps.

@michelle thanks for the reply, already tried but not worked.