What is TMU (True Mileage Unknown)?

The dealer/seller knows, or shouldknow, whether or notthe odometer on the vehicle does not indicate actual mileage, has been rolled back or otherwise altered to show fewer miles, or replaced with an odometer showing fewer miles than actually driven.

TMU is an acronym that stands for True Mileage Unknown.  True Mileage Unknown means that the seller does not know the actual miles that the vehicle has been driven.  When the seller cannot verify that what is on the odometer is correct they have to list that the true mileage is unknown.  Typically this is due to the fact that the odometer failed in some way.  The odometer may have just broken or been disconnected or they are unsure of if it rolled over past the top amount of mileage for that vehicle.  Therefore its the dealer or sellers obligation to state TMU or True Mileage Unknown to the seller so they know that the actual mileage that the vehicle has been driven is unknown.