Amend your 2017 return if you need to change or correct something after you already filed it.
Keep in mind: You have 3 years from the date you filed your 2017 return (or 2 years after you paid the tax due, whichever is later) to file an amended return, which means you don't have to get it done by the April 17 filing deadline. More info
Some people may choose to amend because of tax extenders. They’re certain tax breaks that were included in the Bipartisan Budget Act of 2018 in February and are called tax extenders because they were due to expire after 2016 but were extended through 2017. If you filed your tax return before these tax breaks were available, you can choose to amend your return.
