New program enhancements allow you to begin a refund trace online if you have not received your check within 28 days from the original IRS mailing date. Some of you will also be able to correct or change your mailing address within this application if your check was returned to us as undelivered by the U.S. Postal Service. “Where’s My Refund?” will prompt you when these features are available for your situation.
Where's My Refund?
Internal Revenue Service