I provide a Property Maintenance & Improvements service. When invoicing customers for materials I have in stock, do I record the Category on the invoice as Stock Asset?

Mostly we buy materials for the job and list on the invoice as Cost of Sales, so the expense is directly linked to the invoice. Sometimes, we have items already in stock, maybe where we over-bought for another job. Those items are recorded as Stock Assets when I create the expense. Currently when we use items from stock for a job, I have just been recording it on the invoice as Cost of Sales, but am wondering if I should record it as Stock Asset so it reduces the amount held in Stock Assets. Does that make sense?