classification of an inventory item

@Libbpatt 

Am I understanding correctly that these cards are prepaid and the balance is reduced as they use the machinery?  Does the patient pay to load the card?

If that's the case, when the card is loaded, treat that amount as a liability because you have the patient's money but you owe them the service. Then, when the card is used, you will debit (reduce) the liability and credit (increase) income/sales. 

No.  Payments aren't processed with the card; it's only use is to activate the machinery, and it's a one-use item.  What I want to know is what inventory type should the card be listed as so that inventory will be relieved when the sale is recorded.  Should it be an inventory part, or will it work with a service type?  

Are you paying for the cards, or are they a "no-cost-to-you" item? My assumption is that you do purchase them, so you have an expense and increase in physical inventory. When you sell the service, you are "including" the card as a "no-cost-to-customer" part - correct? I would stock it in as an inventory part. At time you sell the service include the card as a line item on the invoice at time of sale as a zero price to customer.

@Libbpatt 

You would have to tell me more about your process.  IMO the card shouldn't be either an inventory or a service item because you aren't selling the card, you are selling a service.  Based on your description, it's my opinion that the card is just an expense for your business like shopping bags at a grocery store because, again, the card is not the product, the service (use of the machinery) is your product.  Just my $.02.  

Yes, we do purchase the cards, and they have absolutely no other use than as the vehicle by which the customer receives the service they've purchased.  I wouldn't mind not having to track them, but this has been going on for several years now (I currently keep a manual inventory tracker) so they're going to roll into the inventory system along with everything else.  Thanks for your assistance.