Our software does transmit Medicare secondary claims electronically, but I too have never heard of being able to actually submit these on line. In the two states I work between, we can submit claims to Medicaid via their websites, but not to either Medicare Contractors. We also use a wonderful software program called "Remit Data" that pulls all our Medicare secondary claims that have not crossed over, and actually reproduces the remits for us...it's a wonderful AR tool...