When doing our 2018 taxes, I found out about an account that hadn't mailed a 1099-DIV last year. They expected us to log in and download it. I put the amount into my 2017 return to see what the difference would be. I was $1 for my state return and $0 for the federal return for whatever reason. Because it is so small, can I enter it in 2018? Or will I pay penalties for not amending 2017?
You should not include it in your 2018 return. You can amend your 2017 tax return but since it sounds like it would only change the tax by $1 you should just not amend. If the IRS audits (they should just start with a letter saying you owe $1) any penalty is based off the amount due so that could be like $1. You really are better off just waiting to see what the IRS does and then paying the tax right away if they assess a tax.