I can only share with you what I've experienced and have been informed of by DFAS and VA... In June of 2011 the VA and DFAS began a "combined effort" to audit retro payments issued to retirees due to apparent "overpayments" related to CRDP. In short, the VA now sends payment data to DFAS for them to "scrub" to ensure or validate whether or not the Veteran is owed any retro.
In my case, I received two increases in one year... Feb 2011, from 40% to 80%, retro paid within days of the new decision. In Dec. 2011, awarded TDIU and a bunch of other increases but, due to the new audit controls, no retro YET. This action, from my understanding only applies to retirees.
I was informed that it takes only one payment to "activate" the audit process by establishing "payment history"; afterwards, the information regarding retro (if any) is provided to the VA for payment to the Veteran.
CB was given a series of timelines as to when retro would be paid, I was only informed that the process "would not take long".
I've stressed too much over waiting for my last claim to be completed (467 days), I'm not doing that again, if and when it shows up , it shows up.