This is not an uncommon situation. Because a 401(k) plan does not report to the IRS any rollover contributions received by the plan, the IRS sometimes questions that these rollovers were actually completed. You'll need to respond to the IRS with documentation showing that the 401(k) plan received this rollover. This documentation would generally be your 401(k) account statement that shows the transaction consisting of the rollover deposit to your 401(k) account.
