No, CheckFree just writes and mails the checks that you
   electronically ask them to.  They don't aggregate anything.

When I have received a check from CheckFree, the stub listed the
clients that the check was for.  Although only one client was listed,
I assume that if more than one of their clients were trying to pay me
that I would simply have received an aggregate check with a stub
itemizing the individual amounts that the check represented.