Till, In the 'settings > item template > connected with client template' , you have this description in the Billing Addon Documentation: This selection allows you to connect an item template with an ISPConfig client template. This allows automatic billing of ISPConfig client templates using the Billing Module (optional, only for recurring items). If a client is assigned a new template in the ISPConfig client module, then a recurring item is created automatically in the Billing Module based on the template associated to the field Connected with client template. Granted, 'Client-Templates' is now 'Limit-Templates' in the Client module, I am still not enjoying any of the 'automatic' functionality you mention. To me, the above Documentation sentence means that if I create both a 'MAIN' and an 'ADDITIONAL' type(s) in the 'Client > Limit Templates' records of the Client module ... and then assign those to the proper 'MASTER' and 'ADDON' template dropdowns in the 'Client > Limits' tab of the Client module (pressing the 'Add Additional Template' button) ... Then I would 'automatically' see those line items built into the Billing module 'recurring item' list; meaning both the 'main' and the 'addon' template would be referenced in the list and a 'Make Invoices' job would build them into one invoice for that client. The term 'Connected with client template' (in the Billing > item template > item) leads me to think that. I DO see the 'main' client template get replicated (or 'connected') into the billing>recurring items list - but NOT the addon template. Therefore, the only solution (I see) is to go to the 'billing module > item template' and manually create an 'invoice item template' record for the 'addon' template - making sure to tick the 'recurring', 'shop > Addon' and 'shop > Addon of' boxes. Also, the 'Connected with client template' must be pointed to the correct 'client > additional template' record. This is prone to error. If I am correct, the problem this creates is two-fold: 1. It makes the beautiful Billing Module much harder to understand because it puts doubt into the user's mind as to what should be happening. Half of the process is 'automated' (i.e. the 'main' limit-template being linked into a billing module's recurring item list item of the same name AND associated with the correct client) - ready for the 'Make Invoices' job to build it. But the other half is not! Forcing the user to manually build the 'additional template' in the billing module - which can be linked to the client module 'additional template' of the same name. (FYI: Because you do in fact put a link to it inside the 'Connected with client template' dropdown menu in the billing > item template > item form.) Once manually made this way, the 'additional template' will become listed in the billing module > 'recurring item' list and will be used to create a proper invoice when the 'Make Invoices' job is run - but not until then. For me, this added confusion when learning the ISPConfig billing module system. It seems that either the 'additonal templates' need to be automatically made just like the main template is, or the documentation needs to be more clear about the need to add it manually. 2. Personally, I do not think ANY 'Client > Limit Templates' should be manually made in the Billing module > Item Template > Invoice Item Template. Once you enable this (manual) ability it then becomes feasible for the billing and client 'Limit Templates' to be different. That opens the possibility for ISPConfig to be billing one thing and enabling the servers to do another. Obviously, being able to construct recurring and item templates within the Billing module > item template form is critical (i.e. yearly domain registrations, service contracts, etc) - but just not for the limit templates that are also used to control server quotas. Awesome work, Till. Rick PS. For the record, I see no reason why anyone would use WHMCS in conjunction with ISPConfig. At best, it is a black box (ioncube) API with complexity that only the English can imagine and include.