Paying a Little Less in Child Support Than Ordered in Divorce Decree

My question involves child support in the State of: Maryland

My ex wife and I divorced in 2003 at which time I was order though the divorce decree to pay $800 a month in child support. At the time of the divorce I was making more money than my ex wife. In 2008 I retired from the military and the contractual job that I had ended, so my income was substantially less than when the order was put in place. I didn't request a modification but tried to maintain the support off my retirement income. When my ex realized that it was beginning to be a struggle for me she offered to me that I could pay her $100 less in support per month. Unfortunately, I paid her in cash for most of the payments but I did continue on a regular basis pay her $700 (every month!) until this present date. Now my ex wants to go back and collect the "arrears" of $100 from the past four years that I didn't pay. We are both agree that I have paid her the $700 but not the full $800. My ex now makes more money than I do, so I was wondering if she can "as she promises" have the courts garnish my wages even though she suggested I pay her the lesser amount.

You should have sought modification. It sounds like your ex- is going to deny that there was an agreement to modify your support or forgive the difference. Do you have any evidence of an agreement?

Yes, there's an email from her stating that she agreed to the reduction. I gained full time employment again about 2 years ago. But as I stated I continued to pay her $700 just not the full $800. So, should I only be responsible for the arrears for 2 years?