How to manage purchase subscriptions?

I know there is a sale_subsciption module, but I wonder if there is any intention of doing something similar with purchases.
Anyway, I would like to know how purchase subscriptions are supposed to be managed currently in Tryton. For example, if we have a subscription of a software which is supposed to be invoiced every month, should we create just one purchase and manually create every month an invoice and link it with the same purchase?

I do not think it ever happens. The main reason is that it is not Tryton that decides to make the invoice but the supplier.

I do not see the point to link to a purchase. It can only mess-up with its workflow (and it may tries to create credit note for the over invoiced quantities).
For me the workflow is pretty simple, the company receives the invoice, it is encoded as supplier invoice (of course it will be easier to support electronic invoice import like And other way is to duplicate the previously received invoice from the supplier and adapt the dates.

Thats what we do for all our recurring expenses and its pretty easy to enter new invoices. Duplicate, edit and post its no more than 10 clicks.

Thanks you both for the replies, I will do it that way.

That’s right, but the supplier makes the invoice considering an agreement with us. Maybe this agreement could be introduced in Tryton in order to have the control of all subscriptions and check if the supplier is not trying to invoice something that is already expired or with a higher price than it should.

Anyway, now it’s clear how to invoice purchase subscriptions.