Can I ammend 2015 filing to waive the NOL carryback period where I did not on the original filing?

You can choose not to carry back your NOL. If you make this choice, then you can use your NOL only in the 20-year carryforward period To make this choice, you need to attach a statement to your original return filed by the due date (including extensions) for the NOL year . as you did not file this statement on time, you cannot waive the carryback period to 2015.