I've been very impressed so far with this plugin, which almost exactly fits my client's needs.
The one thing that is a huge barrier for us is the way it numbers invoices. UK (and in some EU countries like Germany) legislation states that invoices should have a continuous sequential series. From what I can see the plugin numbers invoices based on the next available post id which is not sequential.
I've managed to fix this by making use of the various filters that I've found, but unfortunately I've run into another stumbling block, and that's that the plugin creates the next year's invoice before the previous one has even been paid. This causes issues because for my client, renewals won't be negotiated until a month before, and means there'll be large gaps in the invoice sequence if he deletes the automatically generated invoices for the next period.
Is there any way to disable the automatic generation of the next invoice or have these invoices generated X number of days before the current subscription period elapses?