The 3 Most Common Mistakes Entrepreneurs Make on Their Taxes CPAs reveal the big IRS no-no's committed by 'treps

With corporate tax season upon us, I was curious about the most common--and costly--mistakes entrepreneurs make that could affect their personal finances. So I polled 25 CPAs around the U.S. to find out. Beyond the obvious--we keep sloppy records, we mix business and personal expenses--here's what they had to say.

Misclassifying workers. This issue comes up when independent contractors you've hired are determined by the state to be employees and therefore subject to minimum wage and overtime pay, unemployment insurance, payroll taxes and workers' compensation.

"Unfortunately, there are no hard and fast rules on when an independent contractor must be considered an employee, and the nuances vary state by state," says Jessie Seaman of the Tax Defense Network, a Jacksonville, Fla., firm that specializes in tax disputes.