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 Singapore of assessment is based on income earned in the preceding calendar year. Taxation is based on the source principle, in which only income earned at source, in this case in Singapore, or those derived from overseas but received in Singapore, are taxable. Any income arising from sources outside Singapore and received in Singapore on or after 1 January 2004 by an individual (other than partners of a partnership) is exempt from tax. This system has the potential to allow for tax avoidance practiced by individuals who derive income from abroad, gain tax exemptions via their non-resident status there, and use