Marginal Tax Rate vs Tax Credit
Marginal Tax Rate and Tax Credit are two Public Finance & Taxation concepts in AP Economics that students often mix up. The marginal tax rate is the tax rate applied to the next dollar of income earned. A tax credit directly reduces the amount of tax owed, dollar for dollar. Here is how they compare side by side.
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.
It is more valuable than a deduction of the same size, which only reduces taxable income. Refundable credits can even produce a payment if they exceed the tax owed. Examples include the Earned Income Tax Credit.
Marginal Tax Rate vs Tax Credit: A Price on the Next Dollar Against a Subtraction From the Bill
| Marginal Tax Rate | Tax Credit | |
|---|---|---|
| Where it acts in the calculation | On the income being taxed, setting the charge on each next dollar | On the tax owed, after the schedule has finished working |
| What one extra unit is worth | Determines how much of the next dollar you keep | Cuts tax owed by its face value, whatever rate you face |
| Does your bracket change its value | It is the bracket rate, in the simple case | No, a flat credit is worth the same to a low and a high earner |
| Compared with a deduction | A deduction is worth its size multiplied by this rate | Worth its face value outright, so it beats an equal deduction |
| Effect on the average tax rate | Sets it indirectly through the schedule | Lowers it directly, since the bill falls while income does not |
| Effect on the incentive to earn more | All of it, this is the price charged on extra effort | None if the credit is flat, a large effect once it phases out |
| Can it go below zero | No, a rate applies to income that exists | Yes if refundable, so the household can end the year paid rather than taxed |
A credit is worth its face value, a deduction is worth its size times your marginal rate
The two sit at different points in the calculation, and the gap that opens between them is large. A deduction removes income before the schedule is applied, so what it saves is the deduction multiplied by the rate that income would otherwise have faced. A credit is subtracted from the tax bill after the schedule has finished, so it saves its face value and no rate enters at all. Take a deduction of 600. A taxpayer whose marginal rate is 15 percent saves 90. A taxpayer at 40 percent saves 240, nearly three times as much, from an identical write-off. Now take a credit of 600. Both taxpayers save exactly 600. The deduction is worth more to the higher earner precisely because its value is priced at that earner's marginal rate, while the credit ignores the rate entirely. That single asymmetry settles most design arguments in tax policy. A measure aimed at low earners is written as a credit, since a deduction hands the biggest subsidy to whoever faces the highest rate. A measure meant to change what an activity costs a firm at the margin is more often written as a deduction, because changing the marginal price is the point.
A flat credit moves the average rate and leaves the marginal rate untouched
Suppose someone earning 50,000 owes 8,000 before credits, an average rate of 16 percent. Give them a flat credit of 600 and the bill falls to 7,400, an average rate of 14.8 percent. Ask what happened to the next dollar they earn and the answer is nothing at all. The schedule still charges whatever that dollar was going to cost, because the credit is a fixed subtraction that does not move when income moves. A flat credit therefore redistributes without touching incentives at the margin, which is a rarer property than it sounds, since almost every other instrument does both jobs at once. All of that disappears the moment a credit phases out with income. A credit that shrinks by 20 cents for every extra dollar earned works exactly like a 20 percentage point surcharge on the marginal rate across the phase-out range, even though no statutory rate changed and the taxpayer's bracket is where it always was. See /glossary/earned-income-tax-credit for how far that effect can run. When a question asks about incentives, check whether the credit is flat before assuming the marginal rate equals the schedule rate.
Frequently asked questions
Is a tax credit better than a tax deduction of the same size?
A tax credit of a given size beats a deduction of the same size for every taxpayer, because the credit cancels tax directly while the deduction only removes income from the schedule. A deduction of 600 saves 90 at a 15 percent marginal rate and 240 at 40 percent, while a credit of 600 is worth 600 to both. The gap is widest at the bottom of the income distribution, which is why credits are the usual tool when a policy is aimed at low earners.
Does a tax credit change your marginal tax rate?
A flat credit leaves the marginal tax rate exactly where the schedule put it, because it subtracts a fixed amount from the bill rather than changing what the next dollar costs. Only the average rate falls. A credit that phases out is a different animal, since each extra dollar of income shrinks the credit and the clawback stacks on top of the statutory rate. Someone in a 12 percent band losing 20 cents of credit per extra dollar faces an effective marginal rate of 32 percent.
What happens if a tax credit is bigger than the tax you owe?
A nonrefundable credit stops once the bill reaches zero, so a taxpayer owing 400 who qualifies for a credit of 600 uses 400 and forfeits 200. A refundable credit pays the remaining 200 out as cash, which is what lets a credit reach households with little or no liability. Refundability rather than the headline size of the credit decides whether the poorest claimants receive the full amount, and it is the feature that turns a credit into a transfer.
Get AP Econ exam tips in your inbox
Occasional emails with study tips, new interactive graphs, and exam-season reminders. Free, no spam.
No spam. Unsubscribe anytime. Read our privacy policy.
Keep track of what you have studied
A free EconLearn account adds progress tracking, your quiz history, and achievements. Studying here is free either way, and there is nothing to pay for as a student.
Create a free accountAlready have one? Sign in
Last updated