> When someone in sales issues an invoice with a negative amount
I worked briefly with a tax-saas, and to handle refunds I just... did a negative amount. It worked! Except.... I hadn't looked closely. Their API removed the negative. A charge of -$7.92 was just a charge of $7.92. Their docs indicated "we don't accept negative numbers - use a refund transaction instead" but... the API accepted the negative number, then changed it to a positive, and kept running. No error code returned. Really really poor experience, and I hope they've fixed that.
* Except (these aren't the right thing to do, but I've seen it in the wild many times):
- When someone in sales issues an invoice with a negative amount on line 3. Hey, if I take payments with invoices, why not give back?
- When someone agrees to settle up by providing free services and throws it on the next bill.