Since then, however, he decided not to deduct all of his charitable contributions from his taxable income in 2011 because that would have reduced his tax bill below 13 percent of his total income, aides said. He had said in the campaign that he never paid less than that.

In 2011, the Romney’s charitable cash contributions included $1.115 million to the Mormon church and $214,516 to the Tyler Foundation. The foundation serves families whose children are undergoing treatment at Children’s Hospital Boston and UMass Memorial Children’s Medical Center. The Romneys also claimed a deduction of $920,573 for non-cash contributions that were not spelled out in a statement accompanying the return. The campaign released no other returns but did attempt to explain 20 years of Romney taxes, from 1990 to 2009, in the tax preparers’ letter.

It said the couple owed both state and federal income taxes each year, and the average annual effective federal tax rate was 20.20 percent.

That figure appeared to represent an average of Romney’s tax rates, not the total of taxes paid for the total income over 20 years. It covers years when his salary accounted for a much higher percentage of his income and was taxed at a higher rate than his investment income that mushroomed in later years. The accounting firm said the Romneys paid an effective tax rate of at least 13.66 percent every year. They gave an average of 13.45 percent to charity over the two decades.

Blind trust

A good portion of the Romney fortune has been invested abroad, managed by a blind trust that is out of his control.

The blind trust as of Dec. 31, 2011, held shares of Germany-based sporting goods company adidas, Chinese oil company CNOOC, Russian natural gas powerhouse Gazprom, Japanese carmaker Toyota, German auto giant Volkswagen and foreign banks including Germany’s Deutsche Bank, Brazil’s Itau and the disgraced Swiss bank Credit Suisse, which agreed to a $556 million settlement in 2009 with U.S. authorities who alleged it had help Iran skirt U.S. financial sanctions.

As with the Romneys’ 2010 return, the 2011 return made fleeting mention of a series of offshore investments through tax havens such as the Cayman Islands, Ireland and Luxemburg.

In good health

In addition to the tax information, Romney’s campaign released details about Romney’s health and that of his running mate, Rep. Paul Ryan of Wisconsin.

Dr. Randall Gaz described Romney, 65, as “a vigorous man who takes excellent care of his personal physical health.”

Romney, said Gaz, ”has reserves of strength, energy and stamina that provide him with the ability to meet unexpected demands. There are no physical impairments that should interfere with his rigorous and demanding political career as next president of the United States.“

In a two-page letter, Gaz said Romney takes Lipitor to lower his cholesterol because of a family history of cardiac issues. Gaz also wrote that Romney will undergo close monitoring for prostate cancer because of a family history of the disease.

The doctor noted Romney “eats a high fiber diet with abundant fruits and vegetables and minimizes intake of high cholesterol foods and concentrated sweets.”

Romney’s “slow, resting regular heart rate in the 40s is most likely related to his past intensive exercise with regular running.”

Gaz said his “current medical issues include hyperlipidemia, or high blood cholesterol.”

Ryan’s physician, Dr. Brian Monahan, called his health excellent.

He said Ryan has a history of asthma that is occasionally treated with an inhaler.