The problem is the IRS usually does the "cross check" when there is a distribution that claims prior nondeductible contribution to lower the tax and that can be years later. By that time the taxpayer has long forgotten what they had done in the past but the IRS records for IRA basis go back to 1987.
But do what you want. I go by the IRS rules that say each nondeductible is to be reported on the 8606 for for the year of the contribution. All past years 8606 forms are available on the IRS site.
**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.**
