Under Section 409.008, the requirement to file a DWC-41 is tolled when the employer has knowledge of the injury but does not file a DWC-41. The tolling provision of Section 409.008 does not apply, however, unless there is first the duty to file a DWC-1 pursuant to Section 409.005 (APD 992923 and APD 992963). Here the employer was not required to file a DWC-1 before the claimant was required to file a DWC-41 because the employer had no knowledge of the injury.