A raise that only matches inflation leaves your buying power right where it was. Now imagine your tax brackets stayed frozen. That same raise could push more of your income into a higher bracket, so you'd pay a bigger share in tax while buying nothing extra. Economists call this bracket creep. The tax code mostly blocks it. Mostly.

What bracket creep is

The U.S. federal income tax is progressive. Income gets taxed in layers, and each layer, or bracket, carries its own rate. If the dollar edges of those brackets never moved, inflation by itself would gradually push more of every household's income into the higher layers. Real income would stay the same. Real taxes would go up.

How indexing works

Since 1985, under the Economic Recovery Tax Act of 1981, the federal income tax brackets have been adjusted for inflation every year. Each fall, the IRS publishes the new figures for the coming tax year, covering the bracket thresholds, the standard deduction, and dozens of other amounts.

The measure behind those adjustments changed with the Tax Cuts and Jobs Act of 2017. Beginning with tax year 2018, the IRS uses the Chained Consumer Price Index for All Urban Consumers, or C-CPI-U, in place of the regular CPI-U.

Why the chained index matters

The Bureau of Labor Statistics built the chained CPI to account for how people swap one item for another when relative prices shift. If beef gets pricey and chicken doesn't, plenty of shoppers start buying more chicken. The chained index picks up some of that switching, and over time it has generally climbed a bit more slowly than the regular CPI-U.

A slower index means bracket thresholds also rise a bit more slowly. Over many years that small gap adds up, and a little more income lands in higher brackets than it would have under the old method. The Congressional Budget Office made this point in a June 2019 analysis of bracket creep: in its long-term projections, the switch to the chained index has a small effect at first that grows over time.

Where bracket creep still happens

Not every dollar figure in the tax code is indexed. A few well-known examples:

  • Taxation of Social Security benefits. The income thresholds that decide how much of a benefit is taxable ($25,000 and $34,000 for single filers, $32,000 and $44,000 for married couples filing jointly, per IRS Publication 915) are written into law and aren't adjusted for inflation. As incomes rise along with prices, more retirees cross them.
  • The Net Investment Income Tax. The 3.8 percent tax kicks in above set income thresholds, such as $200,000 for single filers and $250,000 for married couples filing jointly. The IRS states that these thresholds aren't indexed for inflation.
  • The home sale exclusion. The exclusion of up to $250,000 of gain ($500,000 for many married couples) on the sale of a main home hasn't been indexed since it became law in 1997.

Same mechanism every time: a fixed dollar line meets rising prices and catches more people each year.

A simple illustration

Picture a bracket edge set at $50,000 that never moves. A worker earns $48,000. Prices and wages both go up 5 percent, so her pay rises to $50,400. She can buy exactly what she bought before, yet $400 of her income now sits above the line and gets taxed at the higher rate. With indexing, the edge would have shifted to roughly $52,500, and her tax picture would have stayed about the same. These numbers are only illustrative and don't match any actual bracket.

What the numbers look like today

The IRS's adjustments for tax year 2026, in Revenue Procedure 2025-32, show how far the dollar lines move. The standard deduction for 2026 is $16,100 for single filers, $24,150 for heads of household and $32,200 for married couples filing jointly. The 22 percent bracket begins at $50,400 of taxable income for single filers and $100,800 for joint filers, and the top 37 percent rate starts at $640,600 for single filers and $768,700 for joint filers.

Not every change in those figures comes from inflation, though. The 2025 tax law, which the IRS release calls the One, Big, Beautiful Bill, also amended several amounts. So when you compare one year to the next, separate the changes Congress legislated from the ones the inflation formula produced. The IRS news release and the Revenue Procedure note which is which.

How the IRS calculates the adjustment

The basic method is written into the tax code. For each indexed amount, the IRS compares the average chained CPI for a 12 month period ending in August with the same measure for a base year, then applies that ratio to the base dollar amount and rounds the increase down to the next lowest multiple of $50 ($25 for some married-filing-separately figures), as section 1(f)(7) directs. That rounding is one reason the published figures come out as tidy numbers, and it's why small amounts sometimes stay the same from one year to the next.

Indexing and your paycheck

Withholding tables get updated for the new brackets every January. So most workers first notice indexing as a small change in take home pay, not on their tax return. If your raise roughly matched inflation and your withholding barely changed, indexing is doing its job.

Why it matters for planning

Indexing protects the brackets. Your own financial picture can still drift, though. Fixed thresholds, like the ones listed above for Social Security taxation and the Net Investment Income Tax, catch more people every year. If you're close to one of those lines, project a few years ahead with realistic inflation instead of assuming today's numbers will hold.

How to check your own numbers

The IRS announces the inflation adjustments for each coming tax year, usually in October or November, through a news release and a Revenue Procedure. Lining those figures up year to year is a good way to see how far indexing moved things, and our calculator shows how much prices changed across the same stretch.

Sources

  • IRS, annual inflation adjustments newsroom releases and Revenue Procedures: https://www.irs.gov/newsroom
  • IRS, Publication 915, Social Security and Equivalent Railroad Retirement Benefits: https://www.irs.gov/publications/p915
  • IRS, "Questions and answers on the Net Investment Income Tax": https://www.irs.gov/newsroom/questions-and-answers-on-the-net-investment-income-tax
  • IRS, Publication 523, Selling Your Home: https://www.irs.gov/publications/p523
  • U.S. Bureau of Labor Statistics, Chained CPI questions and answers: https://www.bls.gov/cpi/additional-resources/chained-cpi-questions-and-answers.htm
  • Congressional Budget Office, "How Income Growth Affects Tax Revenues in CBO's Long-Term Budget Projections" (June 2019): https://www.cbo.gov/system/files/2019-06/55368-Bracket-Creep_0.pdf
  • IRS, "IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill": https://www.irs.gov/newsroom/irs-releases-tax-inflation-adjustments-for-tax-year-2026-including-amendments-from-the-one-big-beautiful-bill
  • IRS, Revenue Procedure 2025-32: https://www.irs.gov/pub/irs-drop/rp-25-32.pdf