8.—(1) Where an employer fails to pay the levy for any month in full within the time specified in regulation 3, the Agency may assess the amount of the levy payable by the employer under section 3 of the Act and serve on the employer a notice of assessment of the amount due from the employer for that month.
(2) Where an employer has purported to pay the levy within the time specified in regulation 3, but the Agency assesses that the amount paid is below the amount actually payable under section 3 of the Act, the Agency may serve on the employer a notice of assessment of the shortfall due from the employer.