Effective October 1, 2018, the interest rate for both underpayments and overpayments for the state of Alaska increased from 7.75% to 8.00%. In addition, the following changes, due to become effective January 1, 2019, have already been incorporated:

• California will change from 4.00% to 5.00% for underpayments and 1.00% to 2.00% for overpayments.
• Colorado will change from 7.00% to 8.00% for both underpayments and overpayments.
• Idaho will change from 4.00% to 5.00% for both underpayments and overpayments.
• Kentucky will change from 6.00% to 7.00% for underpayments and from 2.00% to 3.00% for overpayments.
• Missouri will change from 1.30% to 1.50% for overpayments; the rate for underpayments will remain the same at 4.00%.
• New Hampshire will change from 6.00% to 7.00% for underpayments and from 3.00% to 4.00% for overpayments.