Okla. Stat. tit. 85A, § 68

A. Unless an employee gives oral or written notice to the employer within thirty (30) days of the date an injury occurs, the rebuttable presumption shall be that the injury was not work- related. Such presumption must be overcome by a preponderance of the evidence. B. Unless an employee gives oral or written notice to the employer within thirty (30) days of the employee's separation from employment, there shall be a rebuttable presumption that an occupational disease or cumulative trauma injury did not arise out of and in the course of employment. Such presumption must be overcome by a preponderance of the evidence.