IFTA Surcharges Explained: How They Affect Your Quarterly Tax Bill

When you look at the IFTA tax rate table, you'll notice that some states have a single diesel rate while others list a base rate plus one or more surcharges. Those surcharges can add $0.05 to $0.20+ per gallon on top of the base fuel tax — and they show up as separate line items on your quarterly return. If you don't account for them correctly, you'll either underpay (triggering a balance-due notice) or overpay (leaving money on the table).

This guide explains what IFTA surcharges are, which states impose them, how they affect your quarterly tax bill, and how to calculate them correctly on your return.

In this guide, you will learn:

• What IFTA surcharges are and why they exist
• Which states have surcharges vs. base-only rates
• How surcharges appear on your IFTA return
• How to calculate surcharge amounts accurately
• Strategic fueling implications of surcharge states

What Are IFTA Surcharges?

An IFTA surcharge is an additional per-gallon tax that a state or province levies on top of its base fuel tax rate. The base rate is the standard motor fuel tax. The surcharge is a separate levy — sometimes called a "surface transportation surcharge," "petroleum business tax," or simply an "additional tax" — that the state collects alongside the base tax.

Surcharges exist for various reasons. Some states use them to fund specific infrastructure projects. Others created them as politically easier alternatives to raising the base fuel tax rate directly. A few states tie surcharges to wholesale fuel prices, meaning the surcharge amount fluctuates quarterly based on market conditions. The practical effect is the same: you owe more per gallon in states with surcharges than the base rate alone suggests.

Under IFTA, surcharges are reported separately from the base tax. Your return will have separate columns (or separate schedule sections) for base tax and surcharge tax. You calculate each independently using the same mileage allocation but different rates.

How Surcharges Show Up on Your Return

On a standard IFTA return, each jurisdiction has a row showing your miles, taxable gallons, tax-paid gallons, net taxable gallons, and tax due at the base rate. States with surcharges get a second row(or a separate schedule) that repeats the same mileage allocation but applies the surcharge rate instead of the base rate.

Here's how it works in practice. Say you drove 10,000 miles in Indiana during Q1 2026 and your fleet MPG is 6.0. Your taxable gallons in Indiana are 10,000 ÷ 6.0 = 1,667 gallons. You purchased 1,200 gallons in Indiana.

• Base tax: (1,667 − 1,200) × $0.3200 = $149.44 owed
• Surcharge: (1,667 − 1,200) × $0.2600 = $121.42 owed
• Total Indiana tax: $270.86

If you only calculated using the combined rate and didn't split base from surcharge, you'd get the same total. But the IFTA return requires separate reporting. Filing software handles this automatically, but if you prepare your return manually, you must look up both the base rate and the surcharge rate for each applicable state.

States With Surcharges vs. Base-Only States

Not every state imposes a surcharge. The majority of IFTA jurisdictions have a single base rate with no additional surcharge. The following table shows the key states that have surcharges for diesel fuel, alongside examples of base-only states for comparison. Rates shown are representative of Q1 2026 and should be verified against the current IFTA rate table before filing.

Note that New York's surcharge (petroleum business tax) is actually larger than its base rate. This is unusual but reflects how New York structured its fuel taxes historically. California's surcharge similarly accounts for a large share of the total rate due to its excise and sales tax components.

How to Calculate Surcharges Correctly

The calculation method for surcharges is identical to the base tax calculation. You use the same inputs — miles driven, fleet MPG, and gallons purchased — but apply the surcharge rate instead of the base rate. The key steps:

1. Taxable gallons = State miles ÷ fleet MPG
2. Net taxable gallons = Taxable gallons − tax-paid gallons in that state
3. Base tax due = Net taxable gallons × base rate
4. Surcharge due = Net taxable gallons × surcharge rate
5. Total state tax = Base tax + surcharge

Critical detail: The tax-paid gallons (fuel purchased in that state) apply to both the base and surcharge calculations equally. When you buy fuel at the pump in a surcharge state, you're paying both the base tax and the surcharge in the pump price. So your credit applies against both rates.

Full Example: Indiana Q1 2026

A carrier with a fleet MPG of 5.8 drove 15,000 miles in Indiana and purchased 1,800 gallons there.

• Taxable gallons: 15,000 ÷ 5.8 = 2,586 gallons
• Net taxable gallons: 2,586 − 1,800 = 786 gallons
• Base tax: 786 × $0.3200 = $251.52
• Surcharge: 786 × $0.2600 = $204.36
• Total Indiana tax: $455.88

Without the surcharge, Indiana would only cost $251.52. The surcharge nearly doubles the tax liability for this state. This is why understanding surcharges matters — they significantly affect where your money goes each quarter.

Surcharges and Strategic Fueling

Surcharges add complexity to strategic fueling decisions. The general IFTA strategy is to buy fuel in high-tax states (maximizing your per-gallon credit) and minimize purchases in low-tax states. Surcharges amplify this effect.

When you buy fuel in Indiana, your per-gallon credit is $0.58 (base + surcharge combined). When you buy fuel in Texas, your credit is only $0.20 per gallon. Every gallon shifted from Texas to Indiana generates an additional $0.38 in fuel credits — a substantial difference over thousands of gallons per quarter.

However, there's a practical limit. Fuel prices at the pump already include state taxes, so high-tax states tend to have higher pump prices. The net savings from strategic fueling come from the IFTA redistribution math, not from the pump price itself. You're paying more upfront but getting a larger credit on your return that offsets tax owed in low-tax states where you drove but didn't fuel up.

Quarterly Fluctuations in Surcharges

Some state surcharges are fixed by legislation and only change when lawmakers act. Others are indexed to wholesale fuel prices or other economic indicators and adjust quarterly. States with variable surcharges include:

• California: The sales tax component varies with diesel prices
• Indiana: The surcharge adjusts based on a formula tied to statewide fuel consumption and highway funding needs
• New York: The petroleum business tax has a variable component updated periodically
• Kentucky: The supplemental tax is tied to the average wholesale price of gasoline

Because these surcharges can change each quarter, you must verify the current surcharge rate before filing. Using last quarter's surcharge rate is a common error that leads to underpayment or overpayment.

Canadian Provincial Surcharges

Canadian provinces participating in IFTA may also have surcharges or multiple tax components. The treatment is the same: separate reporting of base and surcharge amounts. Keep in mind that Canadian rates are in Canadian dollars and typically expressed per liter rather than per gallon. Your IFTA return handles the conversion if you file through a US base jurisdiction, but verify that your software or manual calculations account for the unit differences correctly.

Common Surcharge Filing Mistakes

Reporting Only the Combined Rate

Some carriers look up the "total" diesel tax rate and enter it as the base rate, ignoring the surcharge line entirely. The return totals may look correct, but the base and surcharge columns won't match the published rates. Jurisdictions that audit will catch this discrepancy.

Applying Surcharges to the Wrong States

Not every state has a surcharge. If you accidentally apply a surcharge to a base-only state like Texas or Ohio, you'll overreport tax owed. Conversely, omitting a surcharge for Indiana or New York means you'll underreport.

Forgetting to Update Variable Surcharges

Copying your spreadsheet from last quarter without updating the variable surcharge rates is a recipe for errors. Even if the base rate didn't change, the surcharge might have.

Mismatched Credits

Your fuel credit in a surcharge state should apply to both the base and surcharge calculations. If you only credit fuel purchases against the base tax and not the surcharge (or vice versa), your net tax will be wrong.

Frequently Asked Questions

Are surcharges included in the pump price I pay at the station?

Yes. When you buy diesel at a truck stop in a surcharge state, both the base tax and the surcharge are included in the per-gallon price. You don't pay them separately at the pump. They only become separate when you file your IFTA return, where base and surcharge are reported on different lines.

Do all fuel types have the same surcharge?

Not necessarily. Some states have different surcharge rates for diesel, gasoline, and alternative fuels. Always check the IFTA rate table for your specific fuel type. The surcharge rates listed in this guide are for diesel only.

Can a surcharge result in a credit (refund) for a state?

Yes. If you purchased more fuel in a surcharge state than your miles consumed (meaning your tax-paid gallons exceed your taxable gallons), you'll have a credit for both the base tax and the surcharge. This works the same as base-rate credits — excess fuel purchases generate a refund.

Do I need to keep separate fuel receipts for base and surcharge taxes?

No. Your fuel receipt shows the total price per gallon, which includes all taxes. The split between base and surcharge is handled when you complete the return using the published rate table. Your receipts just need the standard IFTA documentation: date, location, gallons, price per gallon, and total cost.

How do surcharges affect my overall IFTA liability?

Surcharges increase the total tax rate in the states that impose them. If you drive significant miles in surcharge states but buy most of your fuel in low-tax, base-only states, your overall IFTA bill will be higher. Conversely, if you strategically fuel in surcharge states, the higher per-gallon credit can reduce your net liability.

Bottom Line

IFTA surcharges are straightforward once you understand the structure: they're an additional per-gallon tax that some states layer on top of their base fuel tax. The calculation method is identical to base tax — same miles, same MPG, same fuel credits — just applied at a different rate on a separate line of your return. The states that impose them tend to have higher overall fuel tax burdens, which makes them valuable for strategic fueling but costly if you drive there without fueling. Tools like FleetCollect track your miles automatically and apply the correct base and surcharge rates for each jurisdiction, so you don't have to look them up or worry about quarterly rate changes.