Unstated Interest Paid is the percentage of interest that is assumed paid on an installment sale by the US IRS or Internal Revenue Services. Regardless of actual payment or not, if the interest rate is lower than the specified minimum, it is considered paid off. The calculation of unstated interest is done in the case of a contract that does not have enough interest stated. Federal tax code dictate that the federal rate of interest applicable must be included in the contract when sold properties are on an installment basis.