The deadline to file federal income taxes in the United States for the tax year 2022 (which is typically filed in 2023) is April 17, 2023. However, please note that tax deadlines can sometimes vary slightly, so it is always recommended to verify the exact deadline with the IRS or a tax professional. As for the term "IRS," it refers to the Internal Revenue Service, which is the revenue service of the United States federal government responsible for collecting taxes and enforcing tax laws.