Oracle Internet Expense receipt attachments at line level

We are implementing imaged receipts to enhance our expense report processing.

I'm trying to determine if there is any functionality that requires it to be at one level instead of the other level (header or line).  Or does the functionality allow it to be at either level and pass the requirement for a receipt attachment?

I have searched through the implementation guide and I can't find any information related to the requirements about the level of attachment.

Thanks

Ann