13. AUDIT. You agree that on PGWARE's request you will certify in writing your compliance with the terms of this license, including your use of the Software only on the number of computers licensed. You also agree that we may perform an audit which may include examination of your physical premises with prior written notice, and that any audit conducted will be paid for at your expense including an initial U.S $500 investigation fee. Provided that an audit determines all computer licenses have been legally obtained you will be refunded any audit expenses incurred.