Form letter: refusal of partial payment
Re: Lease Agreement dated _ ("Lease") for _ ("Premises")
Dear _,
Enclosed please find your check number _ dated _ in the amount of $_, which I received on _. This is a partial payment, however, as your current balance due is $_. As I have not agreed to accept partial payment, your tender of such partial payment is hereby rejected. Demand for possession of the premises is hereby made. 
Please be guided accordingly.