It's not clear where you are looking for Schedule C. You will not see the actual Schedule C form in the TurboTax interview. You have to print the tax return or ...
The form is Form SSA-1099 or SSA-1099-SM. Enter it under Federal Taxes > Wages & Income > Retirement Plans and Social Security > Social Security (SSA-1099, RRB-...
For such a small amount I would not bother to file an amended return, even if you could do it for free. The IRS is not going to waste its time and money to coll...
The following is from the IRS Instructions for Form 709.
When To File
Form 709 is an annual return.
Generally, you must file Form 709 no earlier than January ...