Forgot to fill out line 16 on 1040

[User1762419]

I filed via free fillable forms. I got my tax return accepted by the IRS electronically. I somehow forgot to fill out line 16 on the 1040, which is my tax that I owe. Do I need to file an amend? I think once the tax hits, I end up going from a refund to owing money like ~$100 overall. Would they do this themselves or would I need to amend? If so would I need to do so immediately? 

[LoganathanB]

You wait till IRS processes your return. They will send a letter after correcting the tax liability and you can pay the difference.

[User1762419]

I already paid the differnce through IRS direct pay. I won't need to file an amend?

[BillM223]

Check the letter carefully. If it says something like "We have corrected your return..." then you do not have to amend your return, because they did it for you.