Addendum to an Annual Lease agreement

[Pamela Holmes]

I am in the process of evicting my tenants due to no rent payment. The tenant contacted me and said they now have 2 months rents available. This is great, however, my current lease agreement list a $20 late fee. I want to change that to a $75 late fee and include a new rent payment arrangement with 'PayLease.com'. Also, include amount charged for the eviction filing fee of $95. The tenant has agreed, but is this legal to do during the lease term. Also, what kind of paperwork is required to accomplish this task? Thanks in advance for your assistance in this matter.