Angus King, the independent candidate for Maine’s open U.S. Senate seat, released his last seven years’ tax returns Monday while his rivals, who had called for the disclosure, were slower to release their returns.

In the tax years from 2005 through 2011, King paid an effective rate ranging from 20.4 percent to 26.4 percent, according to a summary of his filings. His annual earnings averaged about $570,000.

Democratic candidate Cynthia Dill issued a challenge last week for the three major candidates to release their income tax returns. She and Republican Charlie Summers were critical of King’s delayed response to the challenge.

But both appeared unprepared to release their returns when King suddenly disclosed his at noon Monday.

Dill and Summers made their returns available to the Portland Press Herald on Monday night, too late for a detailed analysis of the data by deadline.

Dill released her 2011 tax return around 8 p.m., three hours after the 5 p.m. deadline she had proposed last week. She did so after several inquiries by the Press Herald.

Summers, who agreed to Dill’s challenge last week, released his returns dating back eight years by 8:30 p.m. Monday.

Patsy Wiggins, a spokeswoman for Dill’s campaign, said Dill originally asked that all three candidates release their returns dating back 10 years at 5 p.m. Monday to an impartial third party.

She said King’s campaign never replied to the request, which led to Monday’s free-for-all.

Wiggins said computer problems stalled the release of older tax returns. Dill’s returns for 2002 to 2010 were issued around 10:15 p.m.

The 2011 return provided by Dill’s campaign showed that she filed a joint return with her spouse, Thomas Clarke. Their gross income for 2011 was $82,442.

Drew Brandewie, spokesman for Summers, said the campaign had hoped to work “in a bipartisan way” with Dill to release the returns simultaneously.

Brandewie said that Summers, who prepares his own taxes, will try at a future date to make public his tax returns for nine and 10 years ago.

Summers, who is Maine’s secretary of state, and his wife, Ruth, filed a joint return in 2011. Tax documents provided by his campaign indicated that the Scarborough couple had gross income of $102,583 last year.

Dill said in issuing the challenge last week that releasing the tax returns would bring “civility and transparency” to a race that has been flooded with money from outside groups. Her request was also a challenge to King, perhaps the wealthiest candidate in a race that has echoed national narratives about income disparity and class warfare.

Dill has repeatedly attempted to cast King and Summers as beneficiaries of a system rigged for the connected and the rich.

According to his tax returns, King’s charitable donations totaled $531,663, a yearly average of $75,952, from 2005 through 2011.

King files his taxes jointly with his wife, Mary Herman.

Their gross income was $490,486, according to their 2011 tax return. They paid $67,817 in taxes last year, for an effective tax rate of 20.9 percent.

King’s highest tax rate over the seven-year period was 26.4 percent in 2009. His gross income that year was $665,485.

King averaged $231,206 in capital gains earnings over the last seven years. He has advocated for income equalization — taxing capital gains at the same rate as income tax.

Dill agrees, while Summers has said that he would vote to repeal the capital gains tax.

King’s seven years of tax returns, compiled by his accountant, will be posted on King’s campaign website.

His Senate Financial Disclosure, released this summer, showed that his investments were valued between $4.8 million and $22.5 million, and that his investment income was $234,000 to $2 million over the roughly 17 months covered by the filing.

The report asks only for a value range for investments and investment income, so those numbers are not as precise as earned income.

Summers and Dill filed their Senate disclosure reports well after the May 15 deadline.

Dill didn’t report making any money as an attorney in 2011 or in 2012 to date, though records from the Maine Board of Overseers of the Bar say she’s authorized to practice.

Dill reported $35,654 in earned income in 2011 and 2012 to date. She had earned $22,711 as a legislator since the start of 2011, along with $5,793 from her work as an adjunct faculty member at Southern Maine Community College in South Portland and $650 as a consulting fee from Common Cause, a national lobbying organization promoting open government.

Summers reported only the $70,000 in salary from his job as Maine’s secretary of state. His office told MaineToday Media earlier this month that his annual salary is $72,727.

Summers also holds one position outside of government, as an adviser to Hope for the Warriors, a North Carolina-based group that provides support to wounded service members. He didn’t report being paid for that work.

Staff Writer Dennis Hoey contributed to this report.

Staff Writer Steve Mistler can be contacted at 791-6345 or at:

smistler@pressherald.com

Twitter: stevemistler

Patsy Wiggins, a spokeswoman for Dill’s campaign, said Dill originally asked that all three candidates release their returns dating back 10 years at 5 p.m. Monday to an impartial third party. She said King’s campaign never replied to the request, which led to Monday’s free-for-all. Wiggins said computer problems stalled the release of older tax returns. Dill’s returns for 2002 to 2010 were issued around 10:15 p.m.