Good news for companies whose employees often misplace meal receipts from business trips: The Internal Revenue Service now allows workers to deduct a set amount for meals each day that they are away from home. The per diem rate, says Michael J. Costello, a partner in the Boston office of Laventhol & Horwath, the accounting firm, is $14 ($9 if the employee stays longer than 30 days in one place). But there is one catch: The per diem rate can be claimed only by employees of the business, not its owners.