A reduction in the value of an asset or earnings by the amount of an expense or loss. Companies are able to write off certain expenses that are required to run the business, or have been incurred in the operation of the business and detract from retained revenues.

For example, if you spend money on dinner to take out a client, that meal is a possible write-off towards your income because you presumably discussed business opportunities during the dinner.

Suppose, for another example, you made a sale on credit to a customer, but two weeks later the client's business declared bankruptcy and became completely unable to pay off the credit account with you. This uncollectible debt would then be written-off by your company and recorded as an expense by accountants.