The phrase "ordinary and necessary expenses" is a tax term relating to what is allowable as a tax deductible business expense. Business expenses are the cost of carrying on a trade or business. These expenses are usually tax deductible if the business is operated to make a profit. To be deductible, a business expense must be both ordinary and necessary. An ordinary expense is one that is common and accepted in the taxpayer's trade or business. A necessary expense is one that is helpful and appropriate in the trade or business. According to the IRS, an expense does not have to be indispensable to be considered necessary. See www.irs.gov.