If this was a return of an excess deferral for an employer sponsored retirement plan, such as a 401(k), then a code 8 (with no other code) is not a retirement distribution reported on line 16. It counts as wages not previously taxed so it is added to line 7 wages on the 1040/1040A form.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**