You are correct, as noted below. Here is what you do now: Without a Form 1099R for 2017, you do not have an ability to add the Form 5329. Keep reading to see what you should do. Plan to mail your return.
If it was withdrawn in 2018 it will be reported on your 2018 tax return. You will receive the Form 1099R in 2018 for the withdrawal, which means you will have two years included on the form for next year.
However, you should file Form 5329 with your 2017 tax return to pay the late penalty OR request the waiver of the excess accumulation penalty on the RMD since you missed the December 31, 2017 deadline (as you indicated).
It is almost impossible to prepare a 5329 form with TurboTax if you do not have a 1099-R to file. You are better off just downloading the forms from the IRS. Only if you have a 2017 1099-R to enter can the 5329 be created. If no 1099-R then also hand fill out the IRS 2017 form and attach it to your 2017 tax return that you will need to mail.
From 5329 instructions: Waiver of tax. The IRS can waive part or all of this tax if you can show that any shortfall in the amount of distributions was due to reasonable error and you are taking reasonable steps to remedy the shortfall. If you believe you qualify for this relief, attach a statement of explanation and file Form 5329 as follows.
1. Complete lines 52 and 53 as instructed.
2. Enter “RC” and the amount you want waived in parentheses on the dotted line next to line 54. Subtract this amount from the total shortfall you figured without regard to the waiver, and enter the result on line 54.
3. Complete line 55 as instructed. You must pay any tax due that is reported on line 55.
The IRS will review the information you provide and decide whether to grant your request for a waiver. Here are links to the 2017 Form 5329 and instructions. See part IX of instructions, page 7.
