I can see where to click to amend my 2015 return, but I do not have that option for 2016. Do I have to wait a certain amount of time before amending?

I have received my 2016 return and need to amend it as certain information was left out. I have read and can see where the option should be to amend for 2016 but it is not there for me. Do I have to wait longer for that option to become available?