You can amend your return, but you do have to wait until you either receive your refund or your payment is processed (if you owed). This is because you want to make sure that you are working from your original return exactly as it was processed by the IRS. But you don't have to wait until after 4/18/17.
Your amended return can't be e-filed. You'll have to print it out and mail it.
See the link below for instructions.
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