Add Bill

hello everyone. I want some suggestions about this. I want to add a bill say invoice. and in that invoice it has many fields (say items)like product_code, qty,discount,price. the user has the ability to add more than one item. now I planned to use the structure like this using foreign key relationship.

Bill model consists of some general details like invoice_no, amount , discount, tax, total amount.

Items model(related using fk with Bill model) consists of individual product details such as product_code, qty,discount, price etc. is there are other possibilities? suggest your idea about this. Thank you.