I need to set up an interest account for notes payable in current liabilites. The interest will be paid in the future. Where does the other half of this transaction go?

Probably Interest Expense. But people always seem to think that there is some account that "goes with" another account and is automatically used whenever you use that other account. That isn't true. It depends upon the entire transaction and what is involved.

There are commonalities, but not definitives.

You're also not being very specific. You're saying an "interest account" "for" notes payable. I'm assuming you mean an "interest payable" account. And that leads to the presumption that you are trying to accrue interest that will be paid in the future, in which case it would be interest expense that goes with it. But since you're not being very clear, that's a lot of presuming on my part. You may not mean that at all.