16. For the purposes of section 54(3) (inducements), the Regulator may not issue a compliance notice in respect of a contravention of that section unless the contravention occurred within—
(a)6 months before the time when a complaint was made to the Regulator about the contravention, or
(b)4 years before the time when the Regulator informed the employer of an investigation of the contravention, if no complaint was made before that time.