An employee has committed misconduct for which you have given him punishment by way of "forfeiture of wages and increments." Now, if you withhold his seniority for promotion, then it will be a second punishment for the same misconduct. Jurisprudence demands that there can be only one punishment for one misconduct. Double punishment for a single fault is in bad taste. You cannot give a second punishment as an afterthought.
Your dilemma is that in the recent past, that employee was found guilty, and you awarded him punishment. Now, how can the same employee be promoted within months? This is what is on your mind. However, while awarding punishment, you or the authorities concerned should have been thoughtful. You could have withheld seniority for, say, 1-2 years. Why should he pay the price for you not being thoughtful?
While delivering justice, there is no place for jealousy. Punishments are called negative discipline. This negative discipline is for reforming the defaulter. Now, if you start giving punishments in installments out of jealousy, this reformation will not take place, and it would defeat the very purpose of punishment itself.
Regards,
Dinesh V Divekar