Dear Anonymous, First, it doesn't cost you anything to request to terminate your probation -- unless you need help preparing the Motion for Early Termination of Probation. Read the page on this site titled "Probation" under the blue heading "Criminal" on the navigation bar.
There are certain things you need to be aware of:
All your fines, costs, restitution, etc. should be paid in full.
You should not have re-offended.
You should have completed at least half of your probationary period.
