New York Times op-ed:  Filling Up on Your Dime, by James Alm (Tulane) & Jay Soled (Rutgers):

The next time you fill up your tank, you should know that the person
next to you might be paying much less than you for gasoline. By
reporting their personal automobile use as a business expense, millions
of drivers are essentially getting taxpayer subsidies for their
gasoline.

The tax code treats expenses incurred in the “ordinary and necessary”
course of doing business as tax-deductible, including costs like
gasoline, tolls, parking and vehicle depreciation. Consider a salesman
visiting a client or a lawyer driving from her office to court.
Depending on factors like her tax filing status, whether she itemizes
her deductions, and whether she is self-employed, her savings could be
as much as 35% — or $1.20 for every $3.50 of gasoline.

The deduction can’t be taken for personal auto usage, like grocery trips, vacation travel and, importantly, commuting. But about 10 million drivers break these rules every year, according to
the IRS. More than 60% of the 16 million
taxpayers who claim business-related auto expenses each year do so
inaccurately. Some errors benefit the government, as when taxpayers
mistakenly classify business-related expenses as personal ones. But the
net result is a loss of about $6 billion in annual tax revenue….

What can be done? Congress can start by simplifying the deductibility
rules and exceptions that currently confront drivers. It should also
require more detailed expense reporting by taxpayers who use their cars
for work; institute stricter requirements for write-offs; cap total
auto-related deductions; and stiffen penalties for violators. (Thanks to
technology, keeping track of business-related auto travel is far easier
now than it was in the 1980s.) Congress might even go further and limit
deductible car expenses to employers who actually own the vehicles in
question and use them almost exclusively for business. These measures
might be unpalatable, especially to some small-business owners, but they
deserve examination.

Beyond the revenue, there is the matter of fairness. Americans who are
already struggling to cover their commuting costs shouldn’t have to pay
even more at the pump to subsidize those motorists who are filling up on
their dime.

(Hat Tip: Mike Talbert.