An automatic change in a Social Security rule may sting in 2017.

It’s tax time again, and President-elect Donald Trump and his fellow Republicans in Congress have promised to slash them - especially for corporations and the rich. For millions of Americans, however, a tax increase will be the first thing they see.

About 12 million workers will pay more this year because of an automatic adjustment in their payroll taxes. Unlike previous years, this rise in the Social Security “taxable minimum” - the amount of income subject to tax - is a whopping 7.3%, the most in 34 years. That could cost each affected worker as much as $539, and much more if they’re self-employed.

WHAT’S CHANGING THIS YEAR?    Workers at the top of the income spectrum pay Social Security payroll taxes only on a portion of their wages. For the past 2 years, only the first $118,500 of earnings was subject to the 6.2% tax. In 2017, this taxable minimum jumps to $127,200.

HOW MUCH COULD THIS COST ME?    If you make less than $118,500, you won’t notice a difference. If you earn more, an extra $8,700 could now be subject to the 6.2% Social Security payroll tax, costing you as much as $539 more by the end of the year. Employers, who pay their own 6.2 percent tax on payrolls, will see costs rise, too - self-employed workers could see their Social Security tax burden jump to more than $1,000. As always, however, they’re able to deduct the employer portion on their income tax returns.

About $11.6 billion in new tax revenue could come from the change in 2017, the Social Security Administration estimates.

WHY SUCH A BIG INCREASE?    While the Social Security taxable minimum is adjusted annually based on the National Average Wage Index - which was up 3.5% in 2015 (5X greater than inflation) - the real reason for this sudden, steep hike is simply that the government is making up for lost time. The 2017 hike is essentially 2 years of wage gains packed into one, and the wage index rose 3.6% in 2014