Enter your net IFTA tax due and how many months late you are to estimate the penalty (the greater of $50 or 10%) plus monthly interest, and your total amount owed. Built on the 2026 IFTA rate so you know exactly what a late return will cost.
$1,200 net tax due, 2 months late, at 0.75%/month interest:
IFTA late penalties are designed to sting even on small balances. The penalty is the greater of $50 or 10% of your net tax due — so a missed deadline costs at least $50, and on a $2,000 balance it's $200 before interest. On top of that, interest accrues every month until you pay. The longer you wait, the more it grows.
Here's the mistake that catches new owner-operators: if you hold an IFTA license, you must file a return every quarter — even if you drove zero miles or owe zero tax. Skip a "zero-activity" return and you still get hit with the $50 minimum penalty. Filing on time, every quarter, is the only way to avoid it. Our FAQ and the deadline reminders on the main calculator can keep you on schedule.
IFTA interest is reset each January 1 to the IRS Section 6621 underpayment rate plus 2 percentage points, then charged monthly at 1/12 of that. For 2026 that's roughly 9% per year (about 0.75% per month). Strictly, interest is computed per jurisdiction on the tax owed in each — this tool estimates on your total balance, which is very close for planning. Always confirm the current rate at iftach.org.
The cheapest penalty is the one you never get. Calculate your quarterly tax early with the IFTA calculator, check the current rates, and file before the deadline every time.
Q1 → Apr 30 · Q2 → Jul 31 · Q3 → Oct 31 · Q4 → Jan 31, 2027. File on time to avoid the $50-or-10% penalty entirely.