Tenant paid most, not all rent

[Stephanie Preasha]

I have a situation where a long-term tenant paid all but $275 in the rent (total rent is $1775).  My lease states he will be charged $25 each day not paid but does not specify anything about partial payments.  I did let him know he has at least one day of late fees and he states he will get to me ASAP.  I wouldn't have accepted, however, my tenants pay through Venmo app so I received it whether or not, I accept partial payments.

The last time I spoke to him, he stated he was incapacitated but we did not get into details.  Now his phone goes straight to voicemail.  

What is your procedure for partial payments? I do not want to change utilizing Venmo app as way I received rents because of this.  I will need to add a new clause in lease for this scenario.