Ref. No. 911/14-23B
In the name of Allah the most Gracious the most Merciful
The answer to your question is as follows:
You are already receiving money from government for your work. So, the commission you are taking is a bribe which is extremely prohibited in Islam. It is Haram and a major sin. A Muslim must abstain from taking or receiving bribe.
One who took a bribe while being on job must seek repentance from Allah give back rights to those they belong or give it to the poor without the intention of reward.
The Almighty Allah (saws) has cursed the bribe-giver and taker. (Tirmizi) There is another Hadith which states that the bribe-giver and taker both will go to Hell (Jahannam). May Allah save us all from it. Aameen
ولاتاکلوا اموالکم بینکم بالباطل وتدلوا بھا الی الحکام لتاکلوا فریقا من اموال الناس بالاثم وانتم تعلمون (البقرۃ 188)
And Allah knows best
Darul Uloom waqf Deoband