How do I get the Category to display on Invoice/Order Form

Because of the types of products I have in my store often I will have two or more products with the same name that are different items. Unless I want to check up the model number on each item, a huge time requirement, I need to have the category listed on the invoice/order form. If anyone knows how I can do this your help would be extremely appreciated. Please bear in mind that I have minimal technical knowledge so the more you can dumb it down the better. Also the most ideal way, if possible, is to have it show up under the Products heading as the quantity, then category, dash, product (I need category only, not the subcategories).
Like this: 1 x Product Category-Product Name

Thanks in advance
hbmagiccards

Hi there
Just before you push ahead with this. We have a similar issue however since the model# is always printed on the invoice etc we always use the model# as the identifier for the product. Does this work for you?

Yes, the item id does work for me but the way my business works I have to click on the id number for every product sold in order to know what it is so I can ship it. My solution at present is that I added the category to the id but this is messy and inefficient.

Hi again
I was actually referring to the model number rather then the item number. Because the model number is printed on the invoice, you can display it as part of you product catalogue and it is listed next to every item in the admin view.