Changing date of a validated invoice changes the account, even though it is read-only
Strange but true, after issuing the proforma for an advance payment of 30% on an order, and receiving the payment necessitating changing the date in order to issue the acquitted invoice, the account set for requests for advance payment (4112) changed back to 4111 (French PCG here).
The account (under other information) is read-only when in proforma ('validated' state). In any event, it shouldn't change behind one's back, if it was posted then it becomes a royal PITA to correct.