Unfortunately, you cannot attach other forms and documents to efiled return.
If you need to file other forms and documents with your tax return, you will have to print and file the return/s by mail.
Include the other forms and documents along with a brief explanation of why you are including them.
Are you referring to nonqualified deferred compensation such as here?
See IRS publication 15-A, page 14
“Section 409A provides that all amounts deferred under a nonqualified deferred compensation (NQDC) plan for all tax years are currently includible in gross income……”.
If so, were the benefits distributed by W-2 or 1099-MISC?
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