The post tax portion rolled over to the traditional IRA has become basis in nondeductible traditional IRA contributions. When you eventually take a distribution from your traditional IRAs or otherwise be required to file Form 8606, you'll need to include this basis on Form 8606 line 2 with an explanation that this is basis rolled over from the 401(k). TurboTax allows you to make this entry by clicking the EasyGuide button when making entries related to your traditional IRA contributions and distributions.
