[Sherezada]

Antes de la versión 6.0 es posible cambiar las cuentas a partidas abiertas dejando el saldo de la cuenta en 0.
A partir de la versión 6.0 se tiene que aplicar la nota 1646957 - FI Transaction FS00 Deactivate Open Item Management throws
Resolution


To resolve this issue you have the following options:
1.SAP recommends that you create a new account with the open item management indicator correctly set and transfer the balance from the old account to the new account. Please see steps in KBA 1646466.
2.If the balance on the account is zero. You can follow the steps in note 606977. If anything was ever posted to this account, the message needs to be displayed.
3.Please also review note 175960 the deactivation of the Open Item Management can also be done with the RFSEPA03 (or your 'Z' version of the report). Please note that questions regarding the use of the reports will only be considered as SAP Remote Consultation, since the account change is a correction to an incorrect account control'

No es posible cambiar el flag en la versión 6.0 debido al new general ledgar. Hay otra nota que no encontre en este momento donde te dice que es posible pero a mi usuario no le gusto esa solución.
En resumen cerramos la cuenta y abrimos otra :S