The 2016 1099-R must be reported in the 2016 return, you have to amend 2016 tax filings for that. Basically, you know you will get a 1099 for the year you are working on, so you input it in the year you are filing so you won't have to amend the return. Another note, this is a 2 year old post, so you should start a new post.
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