What is Marginal tax rate?

Your marginal tax rate is the rate you pay on your last dollar of income. It determines how much tax you’d owe on extra earnings. In the United States, federal income taxes are progressive, meaning income is divided into segments, and each segment is taxed at an increasing rate. A taxpayer's marginal tax rate corresponds to the highest tax bracket their income reaches, representing the rate they would pay on any additional income earned.

For example, if a single filer's taxable income reaches the 22% tax bracket in 2026, their marginal tax rate is 22%. Any additional dollar they earn, such as a work bonus or short-term capital gain, will be taxed at 22%, until their income reaches the threshold for the 24% bracket. Conversely, any tax deduction they claim will save them 22 cents for every dollar deducted.

Your marginal tax rate helps you evaluate financial decisions, such as working overtime, investing in taxable vs. tax-exempt bonds, or choosing between a pre-tax traditional 401(k) and an after-tax Roth 401(k). Marginal tax rates only apply to taxable income, after deductions have been subtracted.

When making financial decisions, it is critical to distinguish your federal statutory marginal tax rate from your true effective marginal tax rate. A taxpayer's true marginal rate includes state and local income taxes, FICA payroll taxes (such as Social Security and Medicare), and the phase-out of various tax credits, deductions, and exemptions. For example, if a taxpayer's income reaches the phase-out threshold for the Child Tax Credit or the Student Loan Interest Deduction, earning an extra dollar not only triggers statutory federal tax but also reduces their tax benefits, effectively compounding their tax rate. For high-income earners, earning above $200,000 (single) or $250,000 (joint) triggers the 0.9% <a href="/articles/high-income-fica-additional-medicare-niit-math" class="text-emerald-600 dark:text-emerald-400 hover:text-emerald-700 dark:hover:text-emerald-300 hover:underline font-semibold transition-colors duration-200">Additional Medicare Tax</a> and the 3.8% Net Investment Income Tax (NIIT), raising their marginal rate on earned and investment income, respectively. Calculating this true marginal impact is essential when deciding whether to make traditional pre-tax contributions to reduce current taxable income or to choose Roth options for future tax-free growth.