Would it be possible to change the term of a CD if it was not disclosed at the time it was purchased? We have a 21 month CD that converts at maturity to an 18 month CD. We have a few other 21 month CDs that were sold as 21 month CDs with no conversion at maturity. I'm not sure if this is possible since it seems it would be a matter of contract and not exactly a "subsequent change" under Reg DD. HELP!!

If the 21 mo. CD is to convert at maturity to an 18 mo. CD, I would think that that should have been disclosed at account opening. Why wasn't it? And why would you have a CD that converts to a different term at maturity? That doesn't make a lot of sense to me.
We have run specials before with an odd term, such as 21 months, but they are not automatically renewable...which makes much more sense to me that what you are talking about.

The 21 month CDs that do not convert were opened prior to the "special" 21 month CD that converts to 18 months. Management now wants to convert the original CDs to the same product as the one that converts at maturity. Question still stands, "Can we do it as a 'subsequent change' or will we have to leave them as a 21 month auto renewable?"

My opinion based upon what you have stated is that your contract prevails. Any subsequent action would be in the form of trying to retain deposits by offering the new "special" product or by offering an 18 month CD (in line with the second part of your "special" product).

Are you actually changing the term or is the rate reverting back to the 18month rate? We have specials like this and the term stays the same but the rate reverts back to a lesser rate at maturity.

Look at your contract with the customer. Ours state we can prevent renewal if we tell you 30 days prior to maturity. If you have such a feature, a letter to the customers affected and a change in your system to non renewable would do what you need.