I need to clarify my fab notes and I need to know specifically which IPC document talks about layer to layer registration. I've been through the 6011 & 6012
I don't know if this is what you're looking for but IPC-2222 Section 9.1.5 states the following: The presentation in Table 9-3 is for the tolerance to be applied to the nominal dimension chosen for the location of the lands connector contacts and conductors in relation to the datums. This tolerance includes tolerances for master pattern accuracy, material movement, layer registration and fixturing. I've attached a jpeg of Table 9-3 to this post.