Materials in the Raw By adding the cost of raw materials bought to the raw materials valuation at the start of the accounting period and subtracting the cost of raw materials transferred to work in progress, the value of raw materials at the conclusion of the accounting period is determined. For example, the company's starting inventory was $10,000 on January 1st, $50,000 in raw materials were bought throughout the year, and $45,000 in supplies were given from stores to work in progress. The closing inventory is thus $10,000 + $50,000 minus $45,000, or $15,000, and a physical inventory check would generally corroborate this