Form 4506-C, Request for Transcript of Tax Return, should be submitted to the IRS as soon as possible after the taxpayer signs it. However, the IRS recommends submitting it at least 60 days before the due date of the tax return or tax payment for which the transcript is required. The IRS processes Form 4506-C requests in the order they are received, and it may take up to 60 days for the transcript to be processed and mailed to the taxpayer or their designated third party.