Under Rule 63 of the CCS Leave Rules, the primary obligation of a study leave bond is that the employee must return to duty and serve the required period (typically 3 to 5 years). Since you came back immediately and have been serving continuously for 15 years, you have fulfilled the service commitment requirement of the bond.
Failing to complete the course is technically a breach of condition. However, because you have been in continuous active service for 15 years, the government’s failure to act or initiate recovery proceedings for 15 years can be a defense in your side but remember that under Article 112 of the Limitation Act, 1963, the limitation period for the Government to file a civil suit for recovery is 30 years. Thus, the claim is not time-barred by law yet.
In administrative law, inaction for 15 years while accepting your regular services creates an equitable defense If the government attempts recovery now, courts often view such delayed enforcement as unreasonable, especially when the employee resumed duty and served the department.
Though it is stated in the Study Leave Bonds that the interest is calculated from the date of demand, as no formal demand notice or order of recovery was ever issued to you over the past 15 years, the clock for interest calculation has not started. If a demand is formally made in the future, interest would only begin running from the date of that specific demand notice, not retroactively for the past 15 years.
Under Rule 63, when an employee fails to complete the course of study or submit the required completion/pass certificate, the period of study leave (220 days) that was initially sanctioned as "Study Leave" can be converted/regularised by the competent authority into other leave due and admissible to you at that time (such as Earned Leave or Half Pay Leave). The study leave salary you drew will be adjusted against the EL balance you had accrued. You do not pay out of pocket if you had sufficient leave balances.If the leave cannot be regularised against admissible leave, recovery of leave salary paid during those 220 days is calculated based on the salary prevalent during that specific period 15 years ago, not your current pay scale.
In your reply to the office enquiry you may mention the exact date you resumed duty, that you have completed over 15 years of continuous service since then, and that you returned to work immediately. You may also state that factually the course could not be completed, but highlight that you promptly reported back to duty rather than staying on extended leave. You may also request that the 220 days be regularised against the leave admissible/due as per applicable leave rules if required.