I had similar problem. Did not make an entry for EIP2 and submitted the return. When I found the payment I started an amendment. When I entered the correct EIP2 amount, my refund was significantly reduced to the point where it says I owe the IRS money. To find the place in turbo Tax to make these EIP entries, Go to "Federal Taxes", then to "Federal Review." I'm not convinced Turbo Tax is handling these inputs properly. I'm stuck now, trying to figure out what to do next.
