charge off as
charge (something) off as (something)
To categorize an expense in a particular way, often so that it can be deducted from one's taxes. Don't worry about how much that new desk chair costs, because we can just charge it off as a work expense.
charge something off as something
to consider something a legitimate expense and deduct it from one's taxes; to assign something to the tax loss category in accounting. I will have to charge this off as a loss. Try to charge it off as a business expense.