Marriage penalty
（重定向自Marriage tax）
The marriage penalty in the United States refers to the higher taxes required from some married couples with both partners earning income that would not be required by two otherwise identical single people with exactly the same incomes. Multiple factors are involved, but in general, in the current U.S. system, single-income married couples usually benefit from filing as a married couple because of income splitting, while dual-income married couples are often penalized in comparison. The percentage of couples affected has varied over the years, depending on shifts in tax rates.