<prompt> Human: Ive already filed taxes for the 2015 year. I want to go back and put 5,500 for last years limit, but I dont have an account yet with Vanguard. Would I be able to get it in on time? What do I do about the taxes that Ive already filed? Do I go back and fix it? But I already received my return?  <response>: Yes, you should be able to open the account on time. Roth contributions are post-tax, and have no effect on your tax return, so by all means - go for it, and no need to file anything! 