I live in Connecticut. Is there anyone who can send me a copy of a late rent notice letter?
My courts in Idaho helpfully publish PDFs of 3 Day Pay or Quit notices, that can be downloaded and used. Check to see if you have something similar in your local courts.
Make it look like a scary legal notice -- not a nice letter. You want to get their attention and communicate that you are serious.
Be sure you are serving the notice according to the law. I am able to post my letters on the rental door and then send a copy through the US mail. I then have to have an Affidavit of Service signed and notarized at my bank. The actual steps you use will also be spelled out in CT law.
If you use the posting method, snap a photo of the posted notice. Some LLs use brightly colored paper to shame late payers. I do not believe that is necessary. I post my notices in envelopes taped to the door.
Here it is on page 17.
There are also included instructions on service. Good luck!