Taxable Income

Getting from your income to taxable income takes three moves.

Start with total income and subtract adjustments such as deductible IRA and HSA contributions to reach adjusted gross income (AGI). From AGI, subtract the larger of the standard deduction or your itemized deductions from Schedule A. Then subtract any qualified business income deduction, for owners of pass-through businesses, and the Schedule 1-A deductions for tips, overtime pay, car-loan interest and the senior deduction, each available for 2025–2028 whether or not you itemize. On the 2025 Form 1040 the answer is line 15, and if deductions exceed AGI it is zero, not negative.

For 2026 the standard deduction is $16,100 for single filers and married people filing separately, $24,150 for heads of household and $32,200 for married couples filing jointly. Being 65 or older, or blind, adds $1,650 per condition for a married person, or $2,050 if unmarried and not a surviving spouse. Each person 65 or older can also deduct up to $6,000 through 2028, reduced by 6% of modified AGI above $75,000 ($150,000 joint; married couples must file jointly to claim it), and from 2026 people who don’t itemize can deduct up to $1,000 of cash gifts to charity ($2,000 joint).

The tax brackets apply to taxable income in slices. In 2026 a single filer pays 10% on the first $12,400, 12% on the slice up to $50,400, 22% up to $105,700 and so on, so moving into a higher bracket taxes only the dollars above the line. The rate on your last dollar is your marginal tax rate; total tax divided by income is your effective tax rate.

Not all taxable income is ordinary income. Qualified dividends and long-term capital gains are part of taxable income but taxed at 0%, 15% or 20%, and they are stacked on top of ordinary income. Ordinary income fills the 0% band first: in 2026 that band ends at $49,450 of taxable income for a single filer and $98,900 for a married couple filing jointly. Short-term gains are taxed like wages.

A few taxes use other measures. The 3.8% net investment income tax and the 0.9% Additional Medicare Tax are figured on their own bases, and the alternative minimum tax recalculates income under a parallel set of rules.

The three measures sit one above the other, and each answers a different question. Gross income is everything taxable before any subtraction, leaving out non-taxable income such as gifts, and it mainly decides whether you must file. AGI is gross income minus adjustments, and most credits, deduction limits and income tests read it or a modified AGI built from it. Taxable income is AGI minus deductions, and it sets your bracket and your capital gains rate.

So a deduction taken after AGI, such as the standard deduction, itemized deductions or the senior deduction, lowers your tax but cannot keep you under an income limit like a Roth IRA phase-out or a Medicare surcharge threshold. Only a change that lowers AGI does both.

State returns add another layer. Each state that taxes income writes its own rules for deductions and exemptions, so your state taxable income is usually a different number from your federal one.

Taxable income rarely moves in a straight line. It tends to peak in the late working years, drop sharply after retirement, and climb again once Social Security, pensions and required minimum distributions arrive. Those swings are what make tax planning possible.

In low-income years, often between retiring and claiming benefits, there may be room left in the 10% and 12% brackets or in the 0% capital gains band. A Roth conversion can fill ordinary brackets with income taxed at a known low rate, and tax-gain harvesting can realize gains at 0%. In high-income years the tools run the other way: pre-tax contributions, bunching itemized deductions into one year, or delaying a sale.

The right target is rarely “as low as possible this year.” It is the lowest reasonable tax across all the years together, which means comparing today’s marginal rate with the rate the same dollars would face later, including their effect on Social Security taxation and Medicare premiums.

Most mistakes come from reading one income figure as if it were another, or from treating the brackets as a single flat rate. The costliest version is turning down a raise, bonus or extra shift for fear of a higher bracket: because brackets apply slice by slice, only the dollars above the line pay the higher rate. The real exceptions are cliffs measured on AGI or MAGI, such as the ACA premium tax credit, not the brackets themselves.