I left out one step in the substitute 1099-R since it is a Traditional IRA that was transfer then the IRA/SEP/SIMPLE box shoukd also be checked. (I edited the answer to add that).
I agree with @dmertz and was going to post as an after-thought...are you sure that the Traditional IRA money actually ended up in your employer 401(k) plan and Betterment did not just transfer it to another IRA account which would not help your backdoor roth at all. Check your 401(k) balance.
**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.**
