I left the US on July 1 2018 back to Canada (my home country), I had been in the US since Jan 2015 on TN Visa. For 2018 I am declaring dual-status, filing 1040NR as Return + 1040 as Statement (I was a resident alien Jan1-Jul1 2018, and non-resident alien Jul1-Dec31 2018).
I'm confused what I need to put on the 1040. I already reported all my US income and taxes on 1040NR (My US employment income was Jan1-Jul1 2018, I had no other income from outside sources during this period). Do I basically duplicate what I put on 1040NR and put it on 1040??
Because you left the country ( cancelled your visa ) in the middle of the year you need the form 1040 to cover the world income during the "resident period" and attache the 1040-NR for any US sourced / connected income during the "Non-Resident" period -- thus 1. avoiding a short tax year and 2. protecting any non US sourced/connected income from US taxes. In your case you really could have just used the 1040 ( especially if you met with the INS and got a sailing permit, thus proving that you are no longer a resident alien ) but it may be safer to file the 1040-NR ( even if all zeroes for income ) . Note that you would need to mail in the two returns ( generally stapled together) and note on the 1040 across the top "DUAL STATUS TAXPAYER "