Tax law changes frequently. Each year, the income bands for each tax bracket get adjusted for inflation, meaning they usually move up. For example, in 2021, single filers paid 10% on income up to $9,950 but in 2022 paid 10% on incomes up to $10,275. On occasion, the government changes the number of tax brackets or the tax rate for each bracket. For example, in 2017, the highest tax bracket was taxed at 39.7% but in 2018 the rate dropped to 37%. Of course, they also increase it as well.