Hi ginniek, Yes, you can file your 2018 return even though you haven't yet filed your 2017 return. When you go to efile, it will ask you for last year's AGI. Because you haven't yet filed your 2017 return, you should enter 0 for the agi.
When you are ready to file your 2017 return, you'll need to mail it in as e-file for prior year returns is not available.
