The amount deducted can be for any tax anticipated by the taxpayer. Thus, the tax could be an income tax, or it could be a payroll tax (i.e., social security and Medicare) or it could be a sales tax for goods purchased outside the resident state of the taxpayer and for which no sales tax was paid.
Sometimes, and especially with self-employed individuals, estimated tax payments are paid (typically through the Electronic Federal Tax Payment System) to the U.S. Department of Treasury, or the relevant State Department of Revenue. These estimated tax payments are made because taxpayers generally need to withhold 90% of their total tax liability. If withholding is below what is required, there could be a tax penalty imposed on the taxpayer.
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