The tax shelter battles fought in the first half of this decade have come and gone, and there’s little doubt that the government won. But the Internal Revenue Service’s (IRS) laser-like focus on shelters also left some unfinished business behind.

“When Congress took aim at tax shelters, the IRS moved from a policy under which it was very reluctant to request tax accrual work papers to one where auditors were expected to ask for work product whenever a taxpayer was involved in a suspicious transaction,” says Kevin Kenworthy, a tax partner at Miller Chevalier.