I'm getting "Incorrect syntax near the keyword 'THEN'.". Anyone know what I'm doing wriong here?

SELECT *,
	CASE 

	WHEN PAY_REC = 'REC' AND (NOTSHIP > CASH_BAL OR (NOTSHIP < CASH_BAL AND CASH_BAL > 0)
		THEN CASH_BAL - NOTSHIP
		ELSE 0

	WHEN PAY_REC = 'PAY' AND (NOTSHIP > CASH_BAL OR (NOTSHIP < CASH_BAL AND CASH_BAL > 0)
		THEN CASH_BAL
		ELSE 0

	END AS Ar

FROM Trades