Tax related mandatory text on invoices

Dear all,

I'm located in Europe and there when you issue invoice without taxes, you need to have on your invoice a mandatory text which justity that the invoice has no taxes.

Generally, it's a description of the flow and the fiscal article which refers to this description.

I'm looking for a way to automatize this. Currently it's a manual (with Print messages attached to the customer), but it's not satisfactory.

One additional difficulty is that, with the physical flow becoming more and more complex, one same customer can have different text to be displayed from an invoice to another if the flow is different and the article justifiying the no taxes may be different as well.