The United States federal and state income tax systems are self-assessment systems. Taxpayers must declare and pay tax without assessment by the taxing authority. Quarterly payments of tax estimated to be due are required to the extent taxes are not paid through withholdings. The second and fourth "quarters" are not a quarter of a year in length. The second "quarter" is two months (April and May) and the fourth is four months (September to December).; IRS Publication 505 See the section "When To Pay Estimated Tax". (Estimated taxes used to be paid based on a calendar quarter, but in the 60's the October due date was moved back to September to pull the third quarter cash receipts into the previous federal budget year which begins on October 1 every year, allowing the federal government to begin the year with a current influx of cash.) Employers must withhold income tax, as well as Social Security and Medicare taxes, from wages.; ; IRS Publication 15. Amounts to be withheld are computed by employers based on representations of tax status by employees on Form W-4, with limited government review.Contrast to, e.g., the United Kingdom system in which all withholding amounts are determined by Inland Revenue.
The United States federal and state income tax systems are self-assessment systems. Taxpayers must declare and pay tax without assessment by the taxing authority. Quarterly payments of tax estimated to be due are required to the extent taxes are not paid through withholdings. The second and fourth "quarters" are not a quarter of a year in length. The second "quarter" is two months (April and May) and the fourth is four months (September to December).; IRS Publication 505 See the section "When To Pay Estimated Tax". (Estimated taxes used to be paid based on a calendar quarter, but in the 60's the October due date was moved back to September to pull the third quarter cash receipts into the previous federal budget year which begins on October 1 every year, allowing the federal government to begin the year with a current influx of cash.) Employers must withhold income tax, as well as Social Security and Medicare taxes, from wages.; ; IRS Publication 15. Amounts to be withheld are computed by employers based on representations of tax status by employees on Form W-4, with limited government reviewContrast to, e.g., the United Kingdom system in which all withholding amounts are determined by Inland Revenue.