The state of the union is pretty good, actually, but President Barack Obama has an idea to make it better: taxing Wall Street and the super-rich to make middle-class work even more worthwhile. It’s Piketty with an American accent.OK, that’s a little bit of an exaggeration, but not a huge one. Obama’s State of the Union will call for three new taxes on rentiers, their heirs, and the big banks to pay for tax credits, some new and some not, that will reward work. Here’s how those tax changes would work.1 — End the step-up basis for capital gains. Unless you’ve inherited money, you might not realize that there’s a pretty big loophole that lets heirs avoid a lot of capital gains from ever being taxed. It’s called “step-up basis,” and the Congressional Budget Office estimates it will cost the government about 0.3 percent of GDP, or $667 billion, in tax revenue over the next decade.Here’s how it works. Imagine you bought $1 million worth of stocks that are worth $10 million by the time you pass away. That’s a $9 million capital gain you’d owe tax on, which, at the 23.2 percent rate, works out to a little more than $2 million check for Uncle Sam — unless you leave the stock to, say, your kids. Then it’s as if your capital gain never happened, at least from the taxman’s perspective. That’s because the capital gain your heirs are taxed on isn’t based on the original price, or basis, at which you bought it. It’s based on the base at which they receive it. So, in this case, your kids would owe taxes only on gains above $10 million. This, as you could guess, most helps the people who have the most money to leave to their families.But there would be exceptions to getting rid of step-up basis, of course. Couples, for one, wouldn’t have to pay any capital gains tax until they had both passed away. They also would get a $200,000 capital gain exception that they wouldn’t owe any tax on, in addition to a $500,000 exception for their home. Items such as furniture, clothing and small heirlooms would be exempt, too. Family-owned businesses wouldn’t have to pay any capital gains until or unless the business was sold, and slightly bigger, closely held businesses would have 15 years to pay whatever they owe.