Somebody fix this, please! The current calculation process makes absolutely no sense. Although it doesn't affect the final total owed by the customer, It is misleading, potentially problemsome, and definitely annoying. I'm constantly explaining the issue to observant customers. Plus, it forces me to manually calculate the sales tax paid on every taxable sale--a tedious task that my invoice program should be doing for me.

BAD (current method):

Sub Total: $100.00
Sales Tax (5%): $5.00
Discount (50%): -$50.00
Total: $52.50
Revenue: $52.50 - $5.00 = $47.50

GOOD (proper method):

Sub Total: $100.00
Discount (50%): -$50.00
Sales Tax (5%): $2.50
Total: $52.50
Revenue: $52.50 - $2.50 = $50.00

If, for example, I applied the "BAD" method to every invoice when determining my annual gross revenue, then I would always be under-reporting on my income tax. Or, If I simply looked at the "Sales Tax" line on every invoice when determining how much to pay the comptroller for collected sales tax, I would be overpaying every time. So, the point is that there is no reason whatsoever to calculate the Sales tax before applying the discount.