Beginning January 1, 1991, Colorado discounts their interest rate on underpayments by 3 points if the balance due is paid within 30 days of the deficiency notice. When an underpayment is calculated for a due date after January 1, 1991, the following prompt is displayed:

Instant Interest calculates 30 days after the date entered. If the deficiency is paid off by that date, Instant Interest reduces the interest rate used by 3 points.