You can use left over money within three days of any scheduled event. ***Using left over money in the next month; needs to used within the first three days of the month and, it has to cover the entire cost of the expense. Example, you have $200 left over and you want to deviate on a trip within the first three days of the new month. As long as the deadhead ticket (or ground transportation) is less than or equal to $200, you can use it. When you file your expense report using left over money, you add the DH ticket on to the previous month's expense. In the above example, if the DH ticket was higher than $200, then there would be a negative ( balance due to company) on your expense report.