Income tax in the United States dates. Some states permit related corporations to file combined or consolidated returns. Most states and localities imposing income tax require estimated payments where tax exceeds certain thresholds, and require withholding tax on payment of wages. Puerto Rico is treated as a separate taxing entity from the USA; its income tax rates are set independently, and only some residents there pay federal income taxes (though everyone must pay all other federal taxes). The unincorporated territories Guam, American Samoa, and the Virgin Islands also impose income tax separately, under a "mirror" tax law based on federal income tax law. Proposals have been
Income tax in the United States of certain types of business expenses. Individuals are also allowed credits related to education expenses, retirement savings, child care expenses, some health care premiums, and a credit for each child. Each of the credits is subject to specific rules and limitations. Some credits are treated as refundable payments. Alternative Minimum Tax: All taxpayers are also subject to the Alternative Minimum Tax if their income exceeds certain exclusion amounts. This tax applies only if it exceeds regular income tax, and is reduced by some credits. Additional Medicare Tax: High-income earners may also have to pay an additional 0.9% tax on wages,