H&R Block Inc., the tax preparer whose stock slid 18 percent last month, told investors to ignore speculation that it faces a surge in costs tied to its defunct mortgage business. The shares rose as much as 9 percent, the most in more than a year. Concern about potential losses tied to buybacks of home loans “is not based on fact,” and reserves to protect the company against claims “are adequate,” Chief Executive Officer Alan Bennett said yesterday during a conference call about fiscal first-quarter earnings. The call included repeated queries about claims, which have totaled more than $680 million. “There’s nothing that we’re seeing anywhere that would lead to the kind of phone calls we just listened to other than speculators that, in my mind, have probably sold our stock short and then stirred this up,” Bennett said in an interview after the call. Mortgage buyback claims “are getting better,” he said.