If the IRS is questioning the rollover, perhaps the rollover was to an account in a qualified retirement plan like a 401(k) and not to an IRA. Qualified retirement plans do not report to the IRA receipt of a rollover, so the IRS often questions whether the rollover was truly completed. One generally needs to head off this questioning by the IRS by including an explanation statement indicating that the rollover was completed to a particular qualified retirement plan. When the rollover is instead completed to an IRA, as VolvoGirl said, the IRA custodian issues Form 5498 reporting receipt of the rollover which generally satisfies the IRS.
