you need to file an amended returns for each year. you're suppose to report each transaction on form 8949 which carries to schedule D. for 2017, if there's a net schedule D profit you'll have a balance due. send in the 1040-X with a check. The IRS will bill you for penalties and interest. if there's a net schedule D loss that exceeds $3,000, the excess gets carried forward to 2018. even if if there's a capital loss carryover to 2018 you can file the amended return for 2018 immediately even though it takes the IRS 12 weeks or more to process an amended return. if the IRS want's proof of loss carryover thing they'll notify you . do not include the 2017 1040-X it with the 2018 amended since this will result in confusion.