By Greg Sargent, Washington Post

Citizens for Tax Justice first calculated what Romney would pay in 2013 under current law. That assumes that the Bush tax cuts would expire, driving the 15 percent rate on capital gains up to 20 percent, and that the top rate on other income, including dividends, would go up to 39.6 percent. It also assumes he’d be subjected to health reform’s new Medicare tax on investment income.

Under that regime, Romney would pay an overall tax rate of around 24 percent.

The group then calculated what Romney would pay if his own plan passed. That is, if you kept the Bush tax cuts in place, including keeping the capital gains tax at 15 percent, and scrapped the Medicare tax, as Romney wants to do.

Under that system, Romney would pay a rate of a little under 15 percent — because virtually all his income is from capital gains and dividends.

The group calculates that this means Romney’s plan would give him a tax cut of more than 40 percent.

“This doesn’t even include Romney’s proposal to cut corporate taxes from 35 percent to 25 percent, which would primarily benefit wealthy shareholders like himself,” Robert McIntyre, the director of Citizens for Tax Justice, tells me.