A. An individual who is domiciled in Oregon, unless he a) does not have a permanent place of abode in Oregon; b) maintains a permanent place of abode in a place other than Oregon, and c) spends less than 31 days of a taxable year in Oregon. ORS § 316.027(A)(i)-(iii).
If you made a mathematical error on your return, often times the IRS will automatically fix the error. After correcting the mistake, the IRS will send you a notice that shows the changes made to your return (usually a CP11 or CP12). Before correcting your return for a mathematical error, you may want to call the IRS at 1-800-829-1040 to see if they have fixed it for you.
If you forgot to include a form or schedule to your return, it is very likely that the IRS will send you a notice requesting just the missing form(s) and/or schedule(s) which means you will not need to do anything other than send in the requested items.