Yes, you should amend 2016 and 2017 since the information entered is incorrect before you prepare your 2018 return. Information from 2016 and 2017 might need to carry to 2018, and you need to make sure that the numbers are correct.
If you already filed your return you will need
to wait to see if it was rejected or accepted. If they were rejected you are
able to login to your return to fix what you need to fix and fix the errors
that caused the rejection and refile the return. If your returns were accepted,
then you will need to file an amended return. You should not
try to amend your return until the original return it has been fully processed
and you have received your refund or your payment has cleared.
Amended returns do not “catch up” to your original return and replace them;
they are processed as two separate returns.
Amended returns have to be printed and filed by mail. It can take the IRS
up to 12 weeks or longer to process them. If you are due a larger refund
than on your original return, your amended return should only show the
difference and you will receive a separate check for it. If you owe money
on your amended return, it will show only the new amount owed, you will have to
mail a check with the return. You can check the status of your amended return
by clicking here: https://www.irs.gov/filing/individuals/amended-returns-form-1040-x-/wheres-my-amended-return-1
Click here for amending instructions: https://ttlc.intuit.com/replies/3288565
Yes, you should amend 2016 and 2017 since the information entered is incorrect before you prepare your 2018 return. Information from 2016 and 2017 might need to carry to 2018, and you need to make sure that the numbers are correct.
If you already filed your return you will need
to wait to see if it was rejected or accepted. If they were rejected you are
able to login to your return to fix what you need to fix and fix the errors
that caused the rejection and refile the return. If your returns were accepted,
then you will need to file an amended return. You should not
try to amend your return until the original return it has been fully processed
and you have received your refund or your payment has cleared.
Amended returns do not “catch up” to your original return and replace them;
they are processed as two separate returns.
Amended returns have to be printed and filed by mail. It can take the IRS
up to 12 weeks or longer to process them. If you are due a larger refund
than on your original return, your amended return should only show the
difference and you will receive a separate check for it. If you owe money
on your amended return, it will show only the new amount owed, you will have to
mail a check with the return. You can check the status of your amended return
by clicking here: https://www.irs.gov/filing/individuals/amended-returns-form-1040-x-/wheres-my-amended-return-1
Click here for amending instructions: https://ttlc.intuit.com/replies/3288565