Your CPA is good at their job. The problem is that their job isn’t your cost per mile.
This one is for owner-operators and small fleets, whether you run one truck or a handful.
Most owner-operators assume that because someone “does the books” at tax time, somebody is watching the numbers. Then a broker offers $2.10 a mile and nobody can say whether that load makes money or quietly loses it. The CPA can’t tell you. That isn’t a failure on their part. It’s a gap between two different kinds of accounting, and most small trucking operations only pay for one of them.
What Your CPA Is Hired to Do
A CPA’s core job for an owner-operator is tax preparation and tax planning. That means:
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Filing your return on time and correctly
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Keeping your tax bill as low as the law allows
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Handling depreciation on the truck and trailer
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Working out quarterly estimated payments
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Applying the trucking-specific rules, like the per diem deduction, which lets drivers under DOT hours-of-service rules deduct 80% of meal per diem instead of the usual 50%
All of that looks backward, usually once a year, and it’s organized around what the IRS wants to see. That’s exactly what a tax return should be. It’s just not the same thing as knowing what your truck costs to run.
What Cost Per Mile Actually Needs
Your cost per mile answers a different question: what does it cost me to move this truck one mile, right now? To get a real number you need:
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Miles, loaded and empty, every month
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Fixed costs kept apart from variable costs. The truck note and insurance cost the same whether you run 8,000 miles or 12,000. Fuel and tires don’t.
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Current numbers, reconciled to your settlements and fuel card, not a year-end summary
None of that is on a tax return.
Why the Tax Return Can’t Tell You
There are no miles on it. A Schedule C groups your spending by IRS line items: car and truck expenses, repairs, insurance, depreciation. It says what you spent in total, not what you spent per mile, and it doesn’t separate the miles you were paid for from the ones you ran empty.
Tax depreciation isn’t operating cost. Tax rules can let you write off much or all of a truck’s cost in the year you buy it. That’s a smart tax move, but it makes year one look terrible and the following years look better than they are. Your truck didn’t cost more to run in its first year. The tax treatment just front-loaded the expense. For pricing loads you need the truck’s cost spread over the miles it will actually run.
It shows up too late. By the time a return is filed, the year it describes is over. If your cost per mile crept up from $1.85 to $2.05 in March, a tax return tells you sometime the next spring, after a year of loads priced against the old number.
The Gap Has a Name
What’s missing is operational accounting: monthly books built to answer business questions instead of tax questions. Which customers pay well once deadhead is counted? Did the fuel card discount actually show up? Is the truck getting more expensive to keep on the road? Can you afford a second truck?
That’s bookkeeping work, done every month, and it’s the piece most small carriers skip. They have a CPA for April and nothing for the other eleven months.
Closing the Gap
You don’t need to replace your CPA. You need the monthly layer underneath them:
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Track miles alongside money. If you file IFTA, you’re already recording miles by jurisdiction every quarter. Put the same miles next to your monthly expenses.
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Separate fixed and variable costs so you can see what changes when you run more, or fewer, miles.
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Work out cost per mile every month, on total miles, not just loaded miles.
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Hand your CPA clean books at year-end. Organized books mean a faster, cheaper return and fewer missed deductions.
For more on the pieces behind the number, see Your P&L Is Lying to You, Truck Depreciation Explained and Direct Costs vs. Overhead.
Find Your Number
Start with our free Cost-Per-Mile Calculator. It takes about ten minutes, needs no email, and gives you the number your tax return can’t. Want help reading it? Talk to us.