"They repaid $729 on average, cutting the average refund by about a third.... H&R Block said two-thirds of its filers were overpaid, but a quarter actually overestimated their earnings in 2014 and got more money back from the IRS on their taxes -- tacking on an average of $425 to their refunds. The tax-preparation company said 13 percent of filers got their income estimates spot on."