If you need to submit certain forms (or attachments) with your return, you are still able to electronically file. However, you will need to complete and mail in Form 8453 U.S. Individual Income Tax Transmittal for an IRS e-file Return along with the forms or attachments.
Acceptable attachments to Form 8453 include:
Any documentation required by these forms should also be attached. If you need to attach other forms, statements, or declarations to your Form 1040 you will need to paper file your return as the IRS will not accept them electronically or with Form 8453.
Do not send Forms W-2 to the IRS with Form 8453, keep them for your records. You will only need to send Forms W-2 with the return if you are paper filing.
Form 8453 (with the required forms or supporting documents) must be mailed to the IRS within three business days after receiving acknowledgement that the return was accepted. An electronically transmitted return will not be considered complete until a Form 8453 is received by the IRS.
If you have to mail Form 8453 and have received a Federal Submission ID number instead of a Declaration Control Number, you may simply leave the DCN boxes blank. Complete the rest of Form 8453 and mail it to the IRS at the address provided in your filing instructions.