Filed 1120S for 2017, then IRS notified me S election wasn't effective until 2018

[christsent]

I bought Turbo Tax for business and filed an 1120S for 2017. Then got a notice from the IRS saying that the our S election was effective January 2018. I guess that means for the brief time I was in business in 2017 I was a C Corp?

What do I need to do in turbo tax to get this right?

[Carl]

How many owners of the business? Just you, and you alone? If so, then you will report all business income/expenses on SCH C as a part of your personal 1040 tax return. If you have already filed your 2017 tax return, then you will have to file an amended return to add the SCH C.