If you requested a "return of contribution" and the earnings, in 2019 then you will not receive the 1099-R reporting that until Jan. 2020. Since you received the return before the extended due date (Oct 15, 2019) you met the requirement. When you file the amended return (within 3 years from the original due date) is immaterial. There is no reason to amend now making up a "dummy" 1099-R form prior to receiving the actual 2019 1099-R in Jan. of 2020. (That 1099-R should have a code "JP" in box 7, the returned contribution in box 1 and the taxable earnings in box 2a.)
When you amend 2018 and enter the 1099-R with the code JP, then TurboTax will enter the box 2a amount as taxable income - the return of yiur own contribution is not taxable.
**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.**
