Q:  What is a reasonable and proportional overdraft fee?

A:  As noted in FAQ # III.2 (de minimis), institutions may increase reputational risk when overdraft fees are significantly greater than the amount of the item being cleared. Institutions should review the amount charged for the overdraft payment compared to the amount of the underlying transaction that triggered the overdraft, and assess whether the charge is reasonable and proportionate in comparison. Institutions should consider de minimis limits to reduce the reputational risk of overdraft fees that are disproportionate to the cost of the underlying transaction.

This can be found in FAQ III-3 of the FDIC’s Overdraft Payment Program Supervisory Guidance FAQs.  The FAQs can be found at: http://www.fdic.gov/news/conferences/overdraft/FAQ.html