IRS requesting Schedule C

I own a mixed use townhouse with a shop on the ground floor and a two bedroom flat above. The shop is rented out all year long, while I let out the flat on a short term basis via Airbnb between April to November. My family goes and stays at the flat from time to time during the remainder of the year.

 

I efiled my 2018 taxes which were accepted in March, but I have just received a letter from the IRS requesting a Schedule C. When I did my taxes online using Turbotax, my Airbnb income was declared as foreign earned income (I am a US citizen but live full time in Europe), but the system never asked me to fill out a Schedule C and so it was never submitted. I can fill one out now but I'm wondering if I should have declared the Airbnb income on Schedule E instead, next to my rental income from the ground floor shop. Can someone please shed some insight on this? And if I should have filled out the info on Schedule E, should I now amend my tax return or just submit Schedule C as IRS has requested?

 

You might need to know how much I materially participate in the Airbnb business. Since I don't have a full time job, my main work is the management of my Airbnb. I handle all the bookings/guest communications, purchase supplies, arrange for things to get fixed and do many of the turnarounds. I don't provide breakfast or daily maid service.

 

Any help would be greatly appreciated! Thank you very much.