The couple's income dropped from $5.5m in 2009 and from $2.6m in 2008, a decline the tax documents attribute to slower book sales.
Mr Obama's salary as US president was $395,000.
They paid more than $500,000 in federal and state taxes and donated a total of $245,000 to three dozen charities.
The couple's tax returns, which list Mr Obama's profession alternately as "US president" and "author", were released by the White House on Monday.
Mr Obama wrote his 1995 memoir Dreams From My Father, a 2006 political book The Audacity of Hope and a children's book last year, Of Thee I Sing: A Letter to My Daughters.
The president benefited considerably from low tax rates on high earners enacted into law under his predecessor George W Bush; Mr Obama has pushed for those to be allowed to expire, saying the US cannot afford tax breaks for the rich at a time of high budget deficits.
The couple pay taxes in the US state of Illinois, where they own a home and lived before moving to Washington in January 2009.
The couple donated to three dozen charities. The largest gift, $131,075, went to the Fisher House Foundation, which provides humanitarian assistance to families of wounded US military personnel.
The US median household income is $52,049.
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