When the outstanding advance exceeds what you owe the employee, then the employee must submit cash or a check for the difference in accordance with your policy. Your failure to collect the amount in excess of substantiated expenses will cause a violation of the accountable plan rules contained in the Internal Revenue Code (title 26 of the United States Code).
Code of Federal Regulations
[FTR Amdt. 70, 63 FR 15974, Apr. 1, 1998. Redesignated by FTR Amdt. 108, 67 FR 57967, Sept. 13, 2002]