(1) An employee who is entitled to, or is on, adoptive leave or additional adoptive leave shall cause the employer (or, if aware of a change of ownership of the undertaking concerned, the successor) to be notified in writing of the employee's intention to return to work and of the date on which the employee expects to do so -

(a) where the leave is for a period of 4 weeks or less, at the same time as the employee notifies the employer of intention to take the leave,

(b) where the leave is for a period of more than 4 weeks -

(i) subject to subparagraph (ii), in case the leave is postponed leave, either -

(I) at the same time as the employee notifies the employer under section 11C(4) of intention to take the leave, or

(II) at least 4 weeks before the date of the expected return to work,

whichever is the later,