I have been using classes to track the project cost. Every cost is assigned to a specific class / Project. Since we didn't have to track the inventory and we were using JIT method for purchases, assigning the cost to different projects / class were easy. When the purchasing department generates the LPO, they assign the right class for each and every item and when its converted into a bill by the Accountant, the cost is allocated to the specific project.
But, recently, we decided to maintain the inventory of some of the fast moving items so that we don't have to do regular purchasing for some of the items. we created inventory items and started working in the planned way.
The problem is since this is a bulk purchase and we don't know what quantity we will use for which project, when generating the LPO, we can't assign classes. So, we decided to assign a general class like "Store" and then deduct the inventory when generating the invoice.
Following this led us to 2 issues; one is that the cost is not assigned to the appropriate class/project. This makes it difficult to track the expense of the specific project. Can we re-assign the Cost from "Store" to another class other than go ahead and alter the bill?
My next question is when we generate an invoice, if we add those inventory to the invoice with 0 "zero" value, will it appear in the invoice (we don't want the customer to see this on the invoice as these as not the main item we are selling them). If it appears, what is the solution?
All inventory in stock is on one location, the store as it were, so you do not need a class for that, and in truth it serves no purpose.
Inventory cost gets allocated to a job in one of two ways
use inventory adjust, set the adjusting account to the job expense account, set the class, and lower the qty of items used or
as you say, put the items on an invoice for the job, even if at a zero sales price. One way to do that without the customer seeing all the nitty gritty, is to make what I call a parts invoice. Invoice number with a -P at the end, all inventory is listed at a zero sales price, save. That allocates cost, and allows you to see that items were in fact used for the job.