The Holidays Act does not require you to fill out a form to get your annual holidays. the Act says
Section 18 Taking of annual holidays
(1)An employer must allow an employee to take annual holidays within 12 months after the date on which the employee’s entitlement to the holidays arose.
(2)If an employee elects to do so, the employer must allow the employee to take at least 2 weeks of his or her annual holidays entitlement in a continuous period.
(3)When annual holidays are to be taken by the employee is to be agreed between the employer and employee.
(4)An employer must not unreasonably withhold consent to an employee’s request to take annual holidays.
But it is a requirement of your employer if you are asked to fill out a form. This can be done verbally and doesnt need to be in writing. If you are asking for money instead of taking the holiday, then this section below applies and you do need this in writing
28A Employee may request portion of annual holidays be paid out
(1)An employee may request that his or her employer pay out a portion of the employee’s entitlement to annual holidays.
(2)A request under subsection (1)—
(a)must be in writing; and
(b)may be made on 1 or more separate occasions until a maximum of 1 week of the employee’s annual holidays is paid out in each entitlement year.