R.I. Gen. Laws § 44-40-14: Delinquency — Interest on delinquency — Applicability of payments.

The tax becomes delinquent from and after the last day allowed for filing a return for the generation skipping transfer. If the tax is not paid before it becomes delinquent, it bears interest after this and until it is paid at the rate of twelve percent (12%) per annum. Every payment on the tax imposed by this part is applied, first, to any interest due on the tax, and then, if there is any balance, to the tax itself.