The same situation happens when a family leaves on bad terms. There is usually one more receipt for them. I give a weekly receipt with each payment but I also give an annual statement in January for taxes that summarizes the previous year. Those I just hang onto and wait for them to contact me to get it. There is no way I would pay to send it certified. The law says I have to make it available not jump through hoops to get it to them. All they have to do is pick it up or email me an address for mailing.