PenFed has never requested any verification documentation from me, that I recall.
I joined NFCU when I was in the Marines. But I left them and rejoined many years later. They requested additional verification of my address at that time, which I took to a branch but they also accept scanned documentation. According to the branch, address verification was triggered because I'm now on the other side of the country from their last known address for me.
The thing with NFCU's verification is it's potentially different for everyone. For a new account, they will always verify your identity, address, etc... because of Know Your Customer laws and just basic bank practices. For further membership elegibility verification, it's a crapshoot. Much of the information they need to verify new accounts is available through various public records databases their security team has access to. For most people, that will be all they'll ever need. But the CU does internal account audits on a subset of new accounts (whether it's a random selection or they use an algorithm for selecting audited accounts, I have no idea) and they may request additional verification documents for those accounts. If you don't respond within what they consider a reasonable time, they'll eventually freeze your account.
They do this both because they respect their membership charter and because they are subject to external audits from NCUA to verify they are abiding by their membership charter.
