A u201cbackdoor Roth IRA contributionu201d consists of two parts: 1) a nondeductible Traditional IRA contribution, and 2) a conversion from Traditional IRA to Roth IRA.You will need to report the nondeductible Traditional IRA contribution on Part I of Form 8606 for the year that the contribution was counted under (which is not necessarily the year of the contribution since you can choose to count a contribution before April 15 as for the previous year).You will need to report the conversion to Roth IRA on Part II of Form 8606 for the year the conversion happened in (this is the exact calendar year, you canu2019t choose to count it under a different year).