The IRS Modernized e-Filing (MeF) system allows you to receive notification of federal acceptance or rejection within a few minutes.
When a return is transmitted through the MeF system, notifications of acceptance contain a Federal Submission ID instead of a Declaration Control Number (DCN). This can cause confusion for users who have to mail the federal Form 8453 to the IRS, as the 8453 asks you to provide the DCN for the return in the blank boxes at the top of the form.
Per the IRS:
The Declaration Control Number (DCN) is not used by MeF; therefore these boxes can remain blank on Form 8453 and any other form that has a DCN (such as Forms 8878, 8879 or 9325). MeF uses a Submission ID instead of a DCN and does not require the Submission ID be reported on these forms.
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.