The message you report seeing in the software is a standard set of instructions. Most of the time, you see, when a taxpayer amends their federal tax return, the related state tax return(s) also reflect "changed" numbers -- and so it is the most common occurrence where a federal return and a state return(s) are amended at the same time. Thus, that results in the stock set of instructions you indicate.
However, this is not always true in all cases. In fact, if you've amended your federal tax return, to account for an additional document, an item of income, or deduction, and that changes your federal refund (or liability), but not your state refund (or liability) then you can safely just file your federal amended tax return, Form 1040X, and not the related state amended return.
In other words, you do not need to file an Oregon amended state tax return, if the Oregon tax numbers have not changed (even while the federal numbers have). An amended tax return is required to be filed only when there is an actual change in taxes owed, or a refund due, in that particular taxing jurisdiction. The federal government and the state of Oregon are legally separate taxing jurisdictions.
Thus, as to your original question, if no Oregon amended return is necessary in the first instance, then you don't need to attach anything to it.
If we've misunderstood your question somehow, then please let us know by posting some follow-up clarification.
It may also help you to know that, with amended returns in general, you only need to attach documents and forms that reflect, or are necessary to explain, any actual changes to the original tax return. Hence, if a taxpayer adds a 1099-G to report unemployment compensation, but their W-2 wages are unchanged, then they don't need to attach the W-2 again to their amended return (because it was filed with their original tax return already).
Thank you for asking about this.
