Originally Posted By: COS website
Because of the very high volume of mail received at the Central Administrative Office, as well as the small staff (which has other projects besides processing memberships), it may take some time for the Registered Membership to be processed, and we give 16 weeks as the maximum time (Active Applications may take about a year or longer to be evaluated and for a response to be sent). If you haven’t heard back in more than 16 weeks regarding registration, email us (membership@churchofsatan.com) with the details (your full name, postal mail address [and tell us if there have been any changes], and when you applied), and we’ll look into the situation. We do not track each piece of mail as it arrives, so if you want to be certain that we have received your materials, we suggest you send them with some form of return receipt card, which the post office will return to you, thus confirming to you that we have your mailing. We will not confirm by e-mail receipt of your materials.

NOTE: If you do not include all of the paperwork required, including the copy of your ID, then your membership will not be processed. Once all materials arrive, then the count begins for the 16 week period.
https://www.churchofsatan.com/join-the-cos.php

You would be wise to be certain the post office will forward your mail to any new address in the meantime just to be sure.