That's slightly above the 13.9 percent rate the couple paid for 2010.
The Romneys were to release their full 2011 returns late Friday.
Romney's taxes have emerged as a key issue during the 2012 presidential race. He released his 2010 tax returns and a 2011 estimate in January but has declined to reveal his returns from earlier years.
Romney's fortune and his long association with Bain Capital, the private equity firm he cofounded, have become issues in his campaign against President Barack Obama.
His campaign earlier estimated that Romney would pay about $3.2 million in taxes for last year.
Romney paid about $3 million in federal income taxes in 2010 -- or 13.9 percent.
Critics, including Obama, have urged Romney to release more than just the two years of returns and follow his father's model. When George Romney ran for president, he released 12 years of tax returns.