We keep track of customer contracts through the Contracts module in Odoo. When our customer issues a PO for the contract, we note the number down on the contract. Contracts are invoiced in two ways:
Through a pre-agreed invoicing plan. In that case we make a sales order for each payment and then invoice that order at the agreed date.
Through timesheets.
The "problem" is that the customer PO reference is not carried over from the contract to the sales order/invoice, so we have to manually copy it for each invoice. This is not a big effort, but it can get forgotten, and then it can be a big headache to straighten out afterwards.
We could (and probably will) knock up a small custom module that copies the reference from the contract, but I wanted to check if anyone thinks this could work out of the box or if we have our process set up the wrong way.