Hi Robert,
I am completely new to investing and don't even have a property. But would still love to reply and see if I can help in any way.
First to say, If you haven't already DEF read Brandon Turner "Managing Rental Properties" book. He has so much insights into how to deal with these situations! I found that book to be my guide as I start this journey myself.
As other replies here have mentioned, for options how you have are around
1. Sending to Debt-Collectors (the ones that take the hefty-fee)
2. Small Claims Court (the tenant will most likely receive a judgement to follow them to pay their fees to you, although this will take awhile to work, there is still a chance in the future you will receive a check in the mail - since it will catch up to them)
In addition you have..
3. Bill Repeatedly (Through a Mailing Invoice System) which I believe is a similar to collection agencies (but just another avenue to consider)
4. Negotiate with them - really this could be a considerable option since chances are, out of all these options you still aren't going to get all the money anyway. It would be an option to get them on the phone (if you can) and purpose less than what they owe, so at that point you are receiving something.
As for what Brandon provided in the book. That about sums it up, I do hope this helps. This situations sucks, but ultimately I think everyone has to deal with this at some point "part of the business"
Do yourself a favor and get that book if you haven't already. And I wish you all the best luck!
God bless.