Inventory items and Progress Invoicing

I typically bid jobs as fixed price/lump sum. In the contract, I specify a draw schedule where I get paid some specified amount of money at key milestones in the project. My estimates in QB Desktop 2020 are a mix of inventory items, non-inventory items, and service items (labor). An example of this situation would be the contract (and the estimate in QB) is for $10,000 total. At point A in the project, the client owes me $3,000, point B they may owe me $4,000, and so on until the total contract sum is paid at project completion. The client never sees the details of the estimate, only the contract sum and the scope of work. So if I use 10 feet of an inventory item or 15 feet, it doesn't change the contract sum (ie, doesn't change what I get paid). As I do the project, I keep track of how much of the inventory item I actually use. In order to get that amount of inventory item out of inventory and charged against the job, my solution so far has been to create a sales receipt for that amount of inventory item at $0. But then what to do with the inventory items in the estimate as I progress invoice off the estimate?