Understand the definition of a tax: A tax is a compulsory financial charge or some other type of levy imposed by a government on individuals or businesses to raise revenue.
Analyze each option to see if it involves a compulsory payment to the government.
Option 1: A minimum wage law sets a legal floor on wages but does not involve a payment to the government, so it is not a tax.
Option 2: A sales tax imposed on retail purchases is a mandatory payment collected by the government on the sale of goods, which fits the definition of a tax.
Option 3: A price ceiling on rental housing is a regulation that limits prices but does not involve a payment to the government, and Option 4: A government subsidy is a payment from the government to individuals or businesses, not a tax.