The SCRA delinquency counseling notice should be send out and received by the Servicemember before the account is 45 days past due. Our collection dept has had challenges maintaining current mailing addresses for some servicemembers, since they are often reassigned and relocate. If we send the notice to the most current address we are able to ascertain, but it is returned, have we met our requirements for this? If we keep getting return mail and cannot document a valid mailing address by the 45th day, are we in trouble?

You can't be faulted for trying. When I was in the service, my mail followed me. I may have gotten it a month after it was sent, but it always got to me eventually.

If you are using the last address you had, and no update was sent, you can only be judged as having met your side of the obligation. That said, use caution as you proceed to the next steps in your collection efforts. That is, I would do more with "locators" within the military before I would jump into any court action.