Below, in italics, is a portion of a clause in my lease (Illinois), and I follow it to a "T". You should follow yours also, do not waiver. I charge a $60 late fee (after 5 pm on 5th) plus $5 per day.
You should also follow the rules in your state, for when you can/should serve 5-day notice, and when you start eviction if that is ignored. Step 1 - late fee; Step 2 - 5 day notice; Step 3 - start eviction. And before I get to Step 2, I tell them it's coming, and when.
Payments must be made paid in FULL by 5:00 p.m. on the 5th to avoid the late charges. If rent is not received by the 10th, a Five Day Notice will be served and you will be charged an additional $50 service fee. If rent is not received by the 15th, eviction will begin, and you will be held responsible for all collection, court and attorney fees/costs. Three (3) late rent violations will result in a rent increase of $50 per month to cover additional collection costs.