The following diagnostic is generating: e-file: Form 3468 #1: The IRS-issued registration number must start with either C, P, or T and followed by a letter between A and M. The next three characters can be any combination of uppercase letters, lowercase letters, or digits. Then, followed by two digit characters. The final five characters can be any combination of uppercase letters, lowercase letters, or digits (for example: CM39488B4567, PA1xC11L2312, TBzD9824E3F2