Taxes: The Basics

The US uses a marginal tax system: income is sliced into bands, and each band is taxed only at its own rate. Someone with $60,000 of taxable income — what's left after deductions like the standard deduction — doesn't pay one rate on the full amount — the first slice is taxed at 10%, the next slice at 12%, and so on, only up to wherever their income actually stops.

Run the actual numbers for that $60,000, using the 2024 single-filer brackets (the thresholds are adjusted for inflation every year, so check the current ones). The first $11,600 is taxed at 10%, which is $1,160. The next $35,550, up to $47,150, is taxed at 12%, which is $4,266. The remaining $12,850, up to the full $60,000, is taxed at 22%, which is $2,827. Add the three slices together — $1,160 plus $4,266 plus $2,827 — and the total tax bill is $8,253, not the $13,200 you'd get from applying 22% to the whole amount.

Your marginal rate is the rate on your next dollar earned. Your effective rate is total tax divided by income — a blend of every bracket you passed through on the way up. The effective rate is always lower than the marginal rate, often by a wide margin, because the earlier, lower-taxed slices are still part of the average.

For the $60,000 example above, that's $8,253 in tax divided by $60,000 of taxable income — an effective rate of about 13.8% on taxable income, even though the marginal rate sitting on the last dollar earned is 22%. Measured against total income it is lower still: if this person took the 2024 standard deduction of $14,600, they earned $74,600, and $8,253 is about 11.1% of that. Either way, nobody pays 22% of their income here; the 22% only describes what the next dollar would face.

Both lower a tax bill, and people use the words interchangeably, which is exactly how the confusion starts. A deduction reduces the income that gets taxed in the first place — its value depends on your marginal rate. A credit reduces the tax bill itself, dollar for dollar, regardless of what bracket you're in.

A credit of a given size is never worth less than a deduction of the same size, and for most people it's worth considerably more — which is why the two are worth telling apart rather than treating as synonyms.

Move the slider above across a bracket boundary and watch what actually happens: only the new income above the line gets taxed at the new, higher rate. Every dollar below that line keeps being taxed exactly as it was before. A raise can never leave you with less take-home pay than before it — the closest that folklore gets to true is a raise pushing some benefit with its own separate income cutoff out of reach, which is a real consideration, but a completely different mechanism from the tax bracket itself.

None of the tax owed above gets paid in one lump sum at the end of the year. Instead, your employer estimates it from every paycheck and sends that estimate to the government on your behalf — a process called withholding. Filing a tax return in the spring isn't paying your taxes; it's reconciling the estimate against the real number.

1. 1

   Every paycheck

   Your employer withholds an estimate of tax owed, based on the form you filled out on hiring, and sends it to the government.

2. 2

   Across the year

   Those estimates add up. If they're too high, you've been overpaying all year; if too low, you've been underpaying.

3. 3

   At filing

   Your actual tax bill is calculated from your real income. A refund means you overpaid through withholding; a bill means you underpaid.

A large refund feels like a windfall, and it is treated like one constantly — but it means you handed the government more of your paycheck than you owed, every month, for a year, and got it back with no interest. That's money that could have sat in your own account or emergency fund the entire time instead. The better outcome is a refund close to $0, or a small bill, which means the estimate was accurate and your paycheck reflected what you actually owed as you earned it.