20.—(1) In a case where additional statutory paternity pay is being paid to a person who works during the additional statutory paternity pay period for an employer who is not liable to pay that person additional statutory paternity pay and who does not fall within, as appropriate, regulation 11(1)(b) or regulation 18(1)(b), there shall be no liability to pay additional statutory paternity pay in respect of the week in which the person does that work.
(2) In a case falling within paragraph (1), the person shall notify the person liable to pay additional statutory paternity pay within seven days of the first day during which the former works during the additional statutory paternity pay period.
(3) The notification mentioned in paragraph (2) shall be in writing, if the person who has been liable to pay additional statutory paternity pay so requests.
(4) In a case where an employee does any work on any day, under a contract of service with an employer who is liable to pay that employee additional statutory paternity pay, for not more than ten such days during the employee’s additional statutory paternity pay period, whether consecutive or not, additional statutory paternity pay shall continue to be payable to the employee by the employer.