It should be possible to distinguish in invoices whether services are displayed and also billed. Services that should be displayed but not billed have so far been shown in brackets as for the “on demand” flag.

Services that have the “on call” flag could thus either be completely hidden in invoices or placed in brackets and not billed or presented and billed as normal services.

Rename the status “use in next invoice” to “display in next invoice” and then add an additional attribute “bill to invoice”, which can be set either or not. It should look like this: