A flat tax is a tax system where the same tax rate is applied to every taxpayer without any deduction or exemption. While it has its advantages, there are also other synonyms for this term, such as proportional tax, single rate tax, or uniform tax. Proportional tax refers to a tax system where the tax rate remains constant, regardless of income level. Single rate tax is a system where there is only one rate for all the taxpayers. While uniform tax refers to a tax system where the same tax rate is applied to all taxpayers, irrespective of their income level, but with certain exemptions and deductions. These synonyms help to illuminate and clarify different aspects of the flat tax concept.