does BRM handle late fees?

Yes, you have two options for handling late fees on BRM.

  1. ad-hoc payment - and then add a reservation note to say what happened.
  2. extra - create an extra (for each type of late return) and set its price accordingly. 

Please note - here is a feature request to officially recognise late fees.  Please vote for it if you like it.  Meanwhile you'll have to use one of the above mechanisms.