Yes, you can file a 2016 amended tax return. If you want to file an amended tax return after IRS accepted your tax return due to a mistake or a missing document, then you will want to wait until your original tax return is processed by the IRS. If you are receiving a refund, you should wait until the check is issued. Amended returns must be filed by mail.
The article below has the specific 2016 instructions to amend a return.