Here is a Quick Fix that works:
Look at Schedule SE Line 3 amount. Multiply that amount times 0.765 and that is the amount you will enter on line 18.
Why 0.765. Well, March 27 to December 31 is 280 days. You will divide the 280 days by 366 days because there was a leap year in 2020 was a leap year.
For example, if $10,000 appears on line 3 of Sch SE, then multiply $10,000 by 0.765. That equals $7650. You enter $7650 on line 18.
