Employee leasing companies seem particularly in the IRS crosshairs.

FORBES: Employers Who Violate Tax Law May Go To Jail

There are Irish employee-leasing companies that supposedly enable high earners to create huge tax-deferred savings plans in Caribbean havens.

FORBES: U.S. tax rackets

Here a dentist, doctor or small-business owner signs an employment contract with a foreign (usually Irish) employee-leasing company, which then leases his services to a U.S. leasing company, which in turn leases his services back to his business or practice.

FORBES: U.S. tax rackets