In order to withdraw an excess Roth contribution, tax free, you have to withdraw the contribution and earnings, by the due date of the tax return for the year in which you made the contribution. If you filed for an extension on your 2015 tax return, then you would have had to have withdrawn the contribution and earnings by the due date of the extension. There will be no tax on the withdrawn contribution but the earnings will be taxable. Additionally, if you did NOT make the withdrawal prior to the appropriate due date, then there is a 6% excise tax. Please refer to page 36 of Pub 590A under "tax on excess contributions" https://www.irs.gov/pub/irs-pdf/p590a.pdf and page 30 of Pub 590B under "withdrawals of contributions by due date" https://www.irs.gov/pub/irs-pdf/p590b.pdf