This no longer works.  We want to issue an invoice with a (hypothetical) charge of $100, with a credit of $5 if the bill is paid before the end of February.

I cannot enter a negative rate of -5.00 as shown in the image from 2020.  I had to enter a negative quantity -1 and a positive charge 5.00 in order to get a negative amount of -$5.00 and a total of $95.  

If I enter 5.00 and then add a negative sign in front of it, Quickbooks clears the negative sign when I tab to the next field.  If I type the negative sign first into a blank rate field, a message pops up in red saying that the value is out of range.  If I persist and enter a qty of 1 and a rate of -5.00 the amount is $0.00, not -$5.00.  I even tried using parentheses to indicate a negative rate.  Same issue.