Never hire a preparer whose fee is tied to the size of your refund. This creates an incentive for them to falsify your return to inflate the total.

A Long Island tax preparer pleaded guilty in January to filing false returns and faces $12 million in restitution. Her clients were charged over $1 million in fees, mainly because she took a percentage cut of the refunds she was inflating with fraudulently claimed credits and phantom dependents. In one instance, an undercover agent hired the preparer to prepare his return. He should have owed the IRS about $205. Instead, the preparer falsified a return that would have indicated a refund of more than $14,000.

Other shady practices covered include "ghost preparers" who refuse to sign the return, preparers who claim work expenses for W-2 employees, and preparers who want you to sign a blank return before they prepare it.