Q4, or the fourth quarter, refers to the last three months of a fiscal year, typically encompassing the months of October, November, and December. This period is crucial for businesses as it often includes significant sales events, such as Black Friday and Christmas, which can greatly impact annual revenue. In financial reporting, Q4 is important for assessing a company's performance over the year. Companies release their earnings reports during this time, providing insights into their profitability and growth. Investors closely monitor these reports to make informed decisions about their investments.