General Principles regulating various types of leave applicable to the central Govt. employees under the CCS (Leave) Rules, 1972 are explained here under.

1.            Right to leave [CCS Leave Rule – 7]
(1)          Leave cannot be claimed as of right.
(2)          When the exigencies of public service so require, leave of any kind may be refused or revoked by the authority competent to grant it, but it shall not be open to that authority to alter the kind of leave due and applied for except at the written request of the Government servant.

2.            Commutation of one kind of leave into another [CCS Leave Rule – 10]
(1)          At the request of a Government servant, the authority which granted him leave may commute (convert) it retrospectively into leave of a different kind which was due and admissible to him at the time the leave was granted, but the Government servant cannot claim such commutation as a matter of right. However, no such request shall be considered unless received by such authority, or any other authority designated in this behalf, within a period of 30 days of the concerned Government servant joining his duty on the expiry of the relevant spell of leave availed of by him.
(2)          The commutation of one kind of leave into another shall be subject to adjustment of leave salary on the basis of leave finally granted to the Government servant, that is to say, any amount paid to him in excess shall be recovered or any arrears due to him shall be paid.

3.            Combination of different kinds of leave [CCS Leave Rule – 11]
Except as otherwise provided in the CCS (Leave) Rules, 1972, any kind of leave may be granted in combination with or in continuation of any other kind of leave. However, Casual Leave which is not recognized as leave under these rules shall not be combined with any other kind of leave admissible under these rules.

4.            Maximum amount of continuous leave [CCS Leave Rule – 12]
Unless the President, in view of the exceptional circumstances of the case otherwise determines, no Government servant shall be granted leave of any kind for a continuous period exceeding five years.

5.            Acceptance of service or employment while on leave [CCS Leave Rule – 13]
Government servants while on leave, other than leave preparatory to retirement shall ordinarily be not permitted to take up any other service or employment. If the grant of such permission is considered desirable in any exceptional case, the Government servant may have his services transferred temporarily from his parent office to the office in which he is permitted to take up service or employment or may be required to resign his appointment before taking up any other service or employment.

6.            Leave not to be granted in certain circumstances [CCS Leave Rule – 17]
Leave shall not be granted to a Government servant whom a competent punishing authority has decided to dismiss, remove or compulsorily retire from Government service.

7.            Commencement and termination of leave [CCS Leave Rule – 21]
Except as provided in Rule 22, leave ordinarily begins on the day on which the transfer of charge is effected and ends on the day preceding that on which the charge is resumed.

8.            Combination of holidays with leave [CCS Leave Rule – 22]
(1)          When the day, immediately preceding the day on which a Government servant’s leave (other than leave on medical certificate) begins or immediately following the day on which his leave expires, is a holiday or one of series of holidays, the Government servant shall be deemed to have been permitted (except in cases where for administrative reasons permission for prefixing/suffixing holidays to leave specifically withheld) to leave his station at the close of the day before, or return to it on the day following such holiday or series of holidays.
(2)          In the case of leave on medical certificate – When a Government servant is certified medically unwell to attend office, holiday(s), if any, immediately preceding the day he is so certified shall be allowed automatically to be prefixed to leave and the holiday(s) if any, immediately succeeding the day he is so certified (including that day) shall automatically be allowed to be suffixed to the leave, and holiday(s), if any, preceding the day he is so certified shall be treated as part of the leave.
NOTE – A compensatory leave granted in lieu of duty performed by a Government servant on Sunday or a holiday for a full day may be treated as a holiday for the above purpose.

9.            Return from leave [CCS Leave Rule – 24]
(1)          A Government servant on leave shall not return to duty before the expiry of the period of leave granted to him unless he is permitted to do so by the authority which granted him leave.
(2)          Notwithstanding anything contained in sub-rule (1), a Government servant on leave preparatory to retirement shall be precluded from returning to duty, save with the consent of the authority competent to appoint him to the post from which he proceeded on leave preparatory to retirement.
(3)          A Government servant who has taken leave on medical certificate may not return to duty until he has produced a medical certificate of fitness as per rule.
(4)          A Government servant returning from leave is not entitled, in the absence of specific orders to that effect, to resume as a matter of course the post which he held before going on leave. Such Government servant shall report his return to duty to the authority which granted him leave or to the authority, if any, specified in the order granting him the leave and await orders.

10.          Absence after expiry of leave [CCS Leave Rule – 25]
(1)          Unless the authority competent to grant leave extends the leave, a Government servant who remains absent after the end of leave is entitled to no leave salary for the period of such absence and that period shall be debited against his leave account as though it were half pay leave, to the extent such leave is due, the period in excess of such leave due being treated as extraordinary leave.
(2)          Willful absence from duty after the expiry of leave renders a Government servant liable to disciplinary action.