I would like to modify my child custody. What qualifies as grounds for modification?

It is not always easy to modify child custody, especially if you and your spouse litigated the issue of custody and a judge made a custody determination. If custody was a litigated issue, the custody agreement that is in place is legally binding and you will have to make a motion to the court to make a change. Whether or not this will be granted depends on whether you have grounds for modification. Whether or not you do have grounds for modification depends on several factors:

• The first thing that the court will consider how long has passed between the creation of the original agreement and the request for modification. Usually, there's a waiting period where the court will be reluctant to make changes. For example, In Illinois, the court will not change a custody agreement within two years of creating it unless it can be proven that there is danger to the child's mental or physical health or well being because of the custody
• The court, if it does decide to consider a petition for a change of custody, will look at whether there has been a material change in circumstance. This can include anything that is significant enough to change the decision the court originally made about custody. One parent trying to move out of state, for example, could be considered a material change. One parent developing an addiction, or being cured from an addiction, can also constitute material changes. Essentially, anything that substantially changes either parent's ability to provide a stable home life is going to be a material change in circumstances. 
• Finally, the decision as to whether to modify a custody agreement is ultimately going to be made in the best interests of the child. If the court believes that it would be better for the child to make a change, then the court will make the modification. 

If you wish to modify child custody, you should strongly consider speaking with a lawyer for help.