leave under paragraph (b) of this section for the period of leave without pay to be taken under
§ 630.1203(a) prior to the date such paid leave commences.  An employee may not retroactively substitute paid leave for leave without pay previously taken under § 630.1203(a).
13.  In § 630.1206, paragraph (f) is revised to read as follows:

§ 630.1206  Notice of leave.
*    *    *    *    *

  (f)  An agency may require that a request for leave under
§ 630.1203(a)(1) and (2) be supported by evidence that is administratively acceptable to the agency.
14.  In § 630.1207, paragraphs (a), (b)(2), (b)(5), (b)(6), (c), and (i) are revised to read as follows:

§ 630.1207  Medical certification.

  (a) An agency may require that a request for leave under § 630.1203(a)(3) or (4)
of this part be supported by written medical certification issued by the health care
provider of the employee or the health care provider of the spouse, son, daughter, or
parent of the employee, as appropriate. An employee shall provide the written medical certification to the agency in a timely manner.  An agency may waive the requirement for an initial medical certificate in a subsequent 12-month period if the leave under § 630.1203(a)(3) or (4) is for the same chronic or continuing condition.
  (b)    *    *    *
  (2)  The probable duration of the serious health condition or specify that the serious health condition is a chronic or continuing condition with an unknown duration and whether the patient is presently incapacitated and the likely duration and frequency of episodes of incapacity;
*    *    *    *    *
  (5)  For the purpose of leave taken under § 630.1203(a)(4), a statement that the employee is unable to perform one or more of the essential functions of his or her position or requires medical treatment for a serious health condition, based on written information provided by the agency on the essential functions of the employee's position or, if not provided, discussion with the employee about the essential functions of his or her position; and
(6)  In the case of certification for intermittent leave or leave on a reduced leave schedule under § 630.1203(a)(3) or (4) for planned medical treatment, the dates (actual or estimates) on which such treatment is expected to be given, the duration of such treatment, and the period of recovery, if any, or specify that the serious health condition is a chronic or continuing condition with an unknown duration and whether the patient is presently incapacitated and the likely duration and frequency of episodes of incapacity.
(c)  The information on the medical certification shall relate only to the