fiscal year. Definition. A 12-month period over which a company budgets its spending. A fiscal year does not always begin in January and end in December; it may run over any period of 12 months. The fiscal year is referred to by the date in which it ends. For example, if a company's fiscal year ends October 31, 2006, then everything between November 1, 2005 and October 31, 2006 would be referred to as FY 2006.