I do have a sort of related question. Is it possible to have a workflow notify if a duplicate # is being used? Apparently users are able to enter the same invoice # (Tranid) on a vendor bill and I am looking for a way to stop that or at least inform the user.

There's a native accounting preference for this

Yup They only had it set to Warn in production.

Note in the case of vendor bills - that check is unique to each vendor

Yea I noticed that. I think they only care about creating the same inv# for the same vendor.