The debate rages on in my cubicle about what the late charge rate is on a dealer direct loan

...is it 5% of the part of the payment that is late..or 5% or a minimum of $15 of the part of the payment that is late..

As I understand it, there is no minimum floor on these loans...

Any thoughts...

I think you need to look at state law. I'm in Oklahoma and our bank uses the following wording:

A late charge on the portion of any payment made more than 10 days after it is due equal to the greater of 5% of the unpaid installment, or the minimum allowed under Oklahoma law, currently $20.00.