Is it possible to change account for all clients

My accountant validates our accounting with his own software. He uses FEC as import file.
He complains about my using of 4111 for all clients, and would like me to change it to 411.
Is there a way to change the Default Account Receivable for the invoices and payments already done?
Because I suppose that the Financial > Configuration > Account configuration will change only further moves…

No, once an invoice is posted you can not change it.
It may be possible to do it using an SQL query but this should be done with care.

They define only the account to be used for new invoices if the party does not have any specific account set. So you should also review that the Parties does not have the account set on it’s form.

So once updated the accounts will be used for new invoices and moves.

What package is your accountant using?
You may wish to remind him that you are using the developed plan and not the abbreviated (or ‘simplified’) plan.
In any event, even the simplified plan can be easily extended towards the developed one.

No possibility to just cheat the names of the accounts ?