There is no reason whatsoever to amend before you receive the actual 1099-R in January. You have until Oct 15, 2019 to *make* the recharacterization but you have 3 years to amend to report it. The 2019 1099-R issued by the IRA trustee is what tells the IRS that you timely did the recharacterization, not your tax return.
If you amend before receiving the 1099-R and the IRA trustee used a different box 7 code, or the box 1 amount is different from what you expect it to be then you would need to amend the amendment which is a sticky process and could not be done utility the first amendment is processed by the IRS which can take 4 or more months. (Even if you mailed an amended 2018 return today it will probably will not be processed until Feb-March, 2020.)
**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.**
