DoninGA's answer applies to regular personal IRA contributions. However, if you are asking about a self-employed retirement contribution, with a timely filed extension request a SEP plan can be established and a SEP IRA account opened and funded up until the extended filing deadline. Similarly, the employer portion of a SIMPLE IRA or Individual 401(k) contribution can also be made up until the extended filing deadline provided that the either of these plans was established prior to the establishment deadline in 2016.
