會計Double-Entry入賬

Why Cr stock in P/L ? Think of the purchases, it is an expense ( Cost of Sales ) of the company. And, purchase account is an expense and it shown in the debit side of the P/L. Actually, the entries should be Cr. Purchase, to reduce the cost and Dr. Stock, the closing inventory, an asset of the company as shown under Current Assets in the Balance Sheet. As the accounts has been closed, we then use the closing approach by Dr. Stock ( Balance Sheet ) and Cr. P/L.
So, the concept is reduce the cost of an expenses $200 as this is an asset $200 of the company at the balance sheet date.