Interest is calculated using the number of calendar days from the original due date of the return until the tax is paid. Interest can be calculated using this formula:
(unpaid tax) x (interest rate) x (number of days) ÷ 365 = Amount of Interest Due
Note: By law, the International Fuel Tax Agreement (IFTA) has a different interest rate. See the instructions for completing Form TC-922, "IFTA/Special Fuel User Tax Return", for the correct interest rate.
| Calendar Year | Interest Rate |
|---|---|
| 2013 | 2% (.02) |
| 2012 | 2% (.02) |
| 2011 | 3% (.03) |
| 2010 | 3% (.03) |
| 2009 | 5% (.05) |
| 2008 | 7% (.07) |
| 2007 | 7% (.07) |
| 2006 | 6% (.06) |
| 2005 | 4% (.04) |
| 2004 | 3% (.03) |
| 2003 | 5% (.05) |
| 2002 | 6% (.06) |
| 2001 | 8% (.08) |
| 1999-2000 | 7% (.07) |
| 1995-1998 | 8% (.08) |
| Oct 12, 1993 – Dec 31, 1994 | 6% (.06) |
| Before Oct 12, 1993 | 12% (.12) |
Note: payments are applied first to penalties, secondly to interest and lastly to tax. See Rule R861-1A-18.