Why is tax missing from this customer's invoice?
Check the saved customer exemption and the tax selections on invoice lines.
QixCount skips invoice tax when the customer's saved exemption is on and passes its expiry check. A blank expiry is treated as no expiry. Also check each invoice line's tax selection; a line without a selected rate may have no calculated tax. This describes the software calculation, not whether an exemption applies to the sale. Read Exemption certificates and Apply tax on invoice lines.