Usage patterns
経費を削減するto cut/reduce expenses
The company reduced business trips in order to cut expenses.
経費がかかるto incur expenses
Opening a new office incurs a lot of expenses.
経費を計上するto book/record as an expense
This cost can be booked as an expense.
経費を精算するto settle/reimburse expenses
After the business trip, I have to settle my expenses.
Expressions
経費で落とすcharge to the company; put on an expense account; write off as an expense