NASHVILLE, Tenn. (AP) — The Internal Revenue Service estimates that 600,000 Tennesseans have waited until April to file their federal income tax returns. The IRS said in a news release Wednesday that Tennesseans have e-filed about 695,000 tax returns from their own computers, up 10.7 percent over this time last year. With the April 18 filing deadline near, the agency said 169,000 taxpayers are expected to request a six-month filing extension.