How should I CMA in this situation?

[AZ-Tax]

2 unrelated taxpayers each shareholders in an S-Corp. We will call them TP1 and TP2. TP2 has a Sch C business that I beleive does business with the S-Corp. TP2 is not real big into organizing for his personal taxes so TP1 is helping TP2 organize but rather then communicating directly with TP2, TP1 wants to communicate with me directly about TP2's form 1040 and related Sch C business. Would a letter signed by TP2 allowing TP1 to fully discuss TP2's personal tax return CMA (cover my a**)? Is there an official form for this and if so what is the form #?

[Uncle Sam]

Tp1/tp2

You've got a conflict of interest situation that requires TP2 to sign a consent form authorizing you to discuss his confidential tax information with TP1. There are plenty
of sources to obtain the standard language for a consent form.
In addition - TP1 ALSO has a conflict of interest situation because his business conducts business with TP2's personal business. So I would suggest that you mention this to TP1 and advise him to obtain a consent form as well.