We have a customer who obtained a car loan prior to joining the military. He has moved to a different state and is 3 months behind on the payments. We noticed that he made a deposit this morning in his checking account that will cover the amount due. Do we have a right to offset in this case? He signed the certified demand letter so we know he has not been deployed to active duty. Thanks so much for your help.

You can use a couple of different DoD sites to validate Active Duty (Moblization/Deployment):
https://www.dmdc.osd.mil/scra/owa/home -OR- https://www.hrc.army.mil/verify

The latter will require that the Service Member register and provide you with a code.

If he signed the demand letter, do you know if that soldier/sailor/airman just happened to be home on leave from a deployment?

Protection is not dependent on location, but service duty. If this person was called to active duty they may be protected under the SCRA. But they also have to request this protection and provide you with a copy of their orders.

The SCRA doesn't say they don't have to pay, nor does it restrict your right to offset. Personally, I'd take the money and apply it against the debt. If this paid it off I'd drag my feet on releasing the title or sending the paid note out until the last minute, in case they do scream through an attorney and you want to negotiate.