Wait until your return is either rejected or approved.
If it's rejected, you can return to your program to add your 1042-S information while fixing the error.
If your return is approved, you would need to amend if adding 1042-S info changes your original refund amount or tax due. Come back later to this link 2018 Amend to amend. If you need to amend, wait until your return is fully processed and you have received your refund or your payment has cleared.
