Marginal Tax Rate
What is Marginal Tax Rate?
The marginal tax rate is the tax rate applied to the next dollar of income earned.
In a progressive system it is the rate of your top bracket. It drives incentives to work and invest because it determines how much of additional income you keep. It is usually higher than the average tax rate.
Marginal Tax Rate: a worked example
A schedule taxes income at 12% up to $40,000 and 30% above that. Dara already earns $38,000 and is offered a contract paying $6,000. The first $2,000 of the fee fills the 12% band, costing $240. The remaining $4,000 is taxed at 30%, costing $1,200. Total tax on the contract is $1,440, so she keeps $4,560, an effective rate of $1,440 ÷ $6,000 = 24% on the extra work. Her marginal rate on the next dollar is now 30%, while her average rate across the full $44,000 is ($4,800 + $1,200) ÷ $44,000 = 13.6%.
The mistake students make with marginal tax rate
Reading your marginal rate straight off the bracket table understates it. Withdrawn benefits and phased out credits stack on top: if a support payment falls by $0.20 for every extra $1 earned, someone in Dara's 30% band faces an effective marginal rate of 50%, keeping $500 of a $1,000 raise instead of $700. Payroll and local income taxes add further layers. What matters for behavior is the total wedge on the next dollar, not the headline bracket number, because that total is what decides whether the extra work is worth taking.
Marginal Tax Rate questions
What is the difference between marginal and average tax rate?
The marginal tax rate applies to your next dollar of income, while the average rate is total tax divided by total income. Dara pays $6,000 on $44,000, an average of 13.6%, yet her next dollar is taxed at 30%. The average tells you what share of your income went to tax; the marginal rate tells you what an extra hour of work is worth, which is the number that changes decisions.
How do you calculate your marginal tax rate?
Marginal tax rate is the change in tax owed divided by the change in income. Add a small amount to your income, recompute the tax, and divide. Dara's $6,000 contract raised her tax by $1,440, which averages 24% over the block, but a block spanning two brackets blends both rates. Shrink the increment to a single dollar and the answer is the rate of the top bracket you reach, 30%.
Why do economists care about marginal tax rates?
Marginal tax rates drive decisions at the margin: whether to take an extra shift, hire another worker, or move savings into a taxable account. What matters for those choices is the share of the next dollar you keep, which is 1 minus the marginal rate. At a 30% rate the keep rate is 70 cents on the dollar; at 50% it is 50 cents, and the extra shift becomes much easier to turn down.
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