All of a country’s citizens pay the government an income tax that is 7% of their annual earnings. This tax is proportional tax.
A proportional tax is understood as an income tax system where the same percentage of tax is levied on all taxpayers, regardless of their income. A proportional tax applies the same tax rate across low, middle, and high-income taxpayers.
As oppose to a proportional tax, the progressive tax system, adjust tax rates by incomes.