Except as provided in paragraph (b) of this section, leave taken under § 630.1203(a) of this part shall be leave without pay.

An employee may elect to substitute the following paid leave for any or all of the period of leave without pay to be taken under § 630.1203(a)—

Accrued or accumulated annual or sick leave under subchapter I of chapter 63 of title 5, United States Code, consistent with current law and regulations governing the granting and use of annual or sick leave;

Advanced annual or sick leave approved under the same terms and conditions that apply to any other agency employee who requests advanced annual or sick leave; and

Leave made available to an employee under the Voluntary Leave Transfer Program or the Voluntary Leave Bank Program consistent with subparts I and J of part 630 of this chapter.

An agency may not deny an employee's right to substitute paid leave under paragraph (b) of this section for any or all of the period of leave without pay to be taken under § 630.1203(a), consistent with current law and regulations.

An agency may not require an employee to substitute paid leave under paragraph (b) of this section for any or all of the period of leave without pay to be taken under § 630.1203(a).

An employee shall notify the agency of his or her intent to substitute paid 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)