The child support laws have changed, and now there is a limit on retroactive support! Beginning on July 1, 2017, a party is limited to five (5) years of support.
The law now reads that "In any action for retroactive child support filed on or after July 1, 2017, retroactive child support shall not be awarded for a period of more than five (5) years from the date the action for support is filed unless the court determines, for good cause shown, that a different award of retroactive child support is in the interest of justice." - TN Code Ann. 36-1-105
If you file, or have filed against you, a child support case after July of this year, the retroactive support (arrears) can't go back past five years unless there is good cause shown to the court for a different about to be ordered.
This changes a long standing rule in Tennessee that retroactive support could date back to the birth of the child, and is less of a burden on the paying parent.