A local landlord has run into a problem with an ex tenant trying to cause problems for him. Among other things, the tenant claims he never received a refund, while the landlord says he sent it but it was never deposited, probably because he had withheld for damages and rent due. Other than getting a receipt upon personal delivery of check, how do you protect yourself from this kind of nonsense?

I always closed the account and have the check made out to the tenant.  If they deposit it, that is the proof. If they claim they didn't get it, then I just go to the bank to verify and if need be, put a stop on the check and have it re-issue.

If the LL actually said he did send and then didn't because he with held....that is jus stupid if he didn't follow the law.

Certified Mail  to their last known address , and their fowarding address .

We use the USPS "Certificate of Mailing" and mail to the address the tenant provides upon vacating, or to their last know address (our rental unit) if a forwarding address was not provided. This covers our end to prove we mailed the letter by the date required for the final report of return of deposit, according to our landlord-tenant law. It costs less than $1.50 (presently $1.35).

If for some reason the tenant did not receive it, we could reissue the letter and refund check. The "Certificate of Mailing" only proves we presented the letter to a post office employee and provides a clearly printed stamp of date it was mailed. We get a copy of it. That is all we need for evidence that we were in compliance with our L-T law as to the date the letter was mailed. We are not required to prove the tenant received the letter. In 20 years of landlording, a tenant has never claimed they did not receive our final letter about the final accounting and security deposit.

Originally posted by @Matthew Paul :

Certified Mail  to their last known address , and their fowarding address .

 Mr. Paul has it absolutely correct. From a legal perspective, keeping receipts from the Trust Account (or wherever you place the money) showing a withdrawal, and then a certified mailing envelope is typical practice. As for whether or not this is the best idea in your jurisdiction, discuss with local attorney. General rule of thumb though; document, document, and then document some more.

All good suggestions so far. I send a final letter with their refund check stating what, if any monies withheld are for. I keep a copy of the letter and a copy of the check when closing out the account. I mail to the forwarding address provided or to the rental address if their mail is being forwarded and a forwarding address wasn't provided. I also send the letter and check via certified mail to make sure I know if and when it was received. It's a very cheap insurance policy to avoid these kinds of things. 

If the tenant hasn't received the check, then a stop payment can be issued and the check can be sent again once the address has been verified. 

This won't help the current situation, but in the future go all electronic. When I refund through erentpayment it's deposited directly into their account with records from them that the transaction occured. No lost in the mail, "I didn't get it", or other BS. Well worth the small fee.