In France, especially when you work for administrations, you first send an estimate, and when you invoice, you HAVE TO indicate the number of the corresponding estimate.

Is there a way to do this? I searched a bit in the database (thanks to SQLite Browser) and I didn't find any link between an invoice and an estimate. I supposed that there were at least links between a working slip and its corresponding estimate slip, but I didn't find anything.

Did I miss something?