(CBS News) -- Mitt Romney is releasing his full 2011 tax returns, which will show he and his wife paid $1,935,708 that year on $13,696,951 of income - a 14.1 percent tax rate.
His campaign also announced that from 1990 through 2009, Romney paid an average annual effective federal tax rate of 20.2 percent.
In 2011, the couple donated 30 percent of their income - more than $4 million - to charity. They claimed a deduction for $2.25 million of those charitable contributions.
That information was revealed in a blog post from Brad Malt, the trustee of the Romney's blind trust. Romney was set to post the full 2011 returns online at 3:00 p.m. Eastern Time, though the page was not loading at that time. The details of Romney's taxes over two decades will be revealed in a notarized letter from the Romneys' tax preparer, PricewaterhouseCoopers, LLP.
Romney previously released his 2010 returns, which showed he paid a 13.9 rate that year on $21.7 million in income. He had also released an estimate of his 2011 returns. Romney, whose net worth is around $250 million, has paid a lower tax rate than many Americans who make less than he does because much of his income comes from capital gains. Such investment income is taxed at a lower rate than wages.
President Obama paid a 26 percent rate in 2010 and a rate of slightly more than 20 percent in 2011. The president has released 12 years of returns, matching the 12 years Romney's father, George Romney, released when he ran for president in 1968.
Democrats have called on Romney to release more than two years of his returns, and some have suggested he is refusing to do so because there were years in which he paid no income taxes in the past. Senate Majority Leader Harry Reid, citing an unnamed Bain Capital investor, has suggested Romney did not pay taxes for a decade.
This release is designed to rebut those claims: Malt wrote that the Romneys owed both state and federal income taxes in each year between 1990 and 2009.
Over the 20 year period, he wrote, the lowest annual rate paid by the couple was 13.66 percent. The couple gave an average of 13.45 percent of their adjusted gross income to charity.
The campaign is also poised to post "physician letters for both Gov. Romney and Rep. Ryan, making public their current state of health," according to Malt's blog post.
The president has attacked Romney over his refusal to release more returns and suggested he uses tax trickery and offshore accounts to reduce his effective rate. A recent Obama campaign ad featured a narrator saying, "Makes you wonder if some years he paid any taxes at all. We don't know because Romney has released just one full year of his tax returns."
Malt's post includes this paragraph: "The Romneys' generous charitable donations in 2011 would have significantly reduced their tax obligation for the year. The Romneys thus limited their deduction of charitable contributions to conform to the Governor's statement in August, based upon the January estimate of income, that he paid at least 13% in income taxes in each of the last 10 years."
In January, Romney said, "I pay all the taxes that are legally required and not a dollar more. I don't think you want someone as the candidate for president who pays more taxes than he owes."
Romney's campaign told CBS News: "He has been clear that no American need pay more than he or she owes under the law. At the same time, he was in the unique position of having made a commitment to the public that his tax rate would be above 13%. He directed his preparers to ensure that he is consistent with that statement."