What is the deadline for making a deductible DB plan contribution? Is it the same as DC.....due by tax filing date, including extensions? I know nothing about DB plans. (I'm not sure I ever want to know much about them either. Yuck) THank you.

Pretty much the same as DC plans, but think more in the line of Money Purchase plans, in that you are covered under IRC 412. This means that you need to get the contribution made no later than 8 1/2 months after plan year end. For your corporate clients this isn't critical since they can't extend out further than that same time frame, but sole props/partnerships can extend out their return to 9 1/2 months. I've seen some people (accountants included) who didn't realize that the funds had to be in 1 month earlier than they were counting on...