User changed the Payment Term in Global Settings > Billing, but the change does not reflect on invoices.
This happens because changing the Payment Term in Global Settings only affects new projects and not existing ones. You should update the Payment Term at the project level in Project Details > General > Billing Options under Terms & Currency in order to reflect it on the project invoices. You can also make a Batch Change to edit the payment terms for all or selected projects (Actions menu). Check out this article for more: Message at the bottom of invoices.