I have been running my S-Corp (just me and my wife, I am 100% owner) since 2009.
I did not invest any money when I started, I did loan to business one time (40k in 2017), and business paid the loan back. All years have been profitable, this is the first year I had a loss to report. Turbotax is asking for Stock basis on form 7203, and the instructions seem all alien to me...
Does Quickbooks (Desktop + Payroll) have some functionality to calculate my Stock Basis?
We're unable to provide such calculations in QBDT Payroll. However, you may check reports like your balance sheet or inventory reports. I also recommend checking with your accountant, so they can help you with the calculation. You can find a ProAdvisor near you.