A Return to Work improvement notice is not invalid merely because of—
(a) a formal defect or irregularity in the Return to Work improvement notice unless the defect or irregularity causes or is likely to cause substantial injustice; or
(b) a failure to use the correct name of the employer to whom the Return to Work improvement notice is issued if the Return to Work improvement notice sufficiently identifies the employer and is issued to the employer in accordance with section 139.