Comment 1 for bug 659540

> Cancelling invoices must lead to an additional move with
> move_lines which revert the original move_lines.
> This and only this is the "normal" way which is accepted by
> fiscal authorities (at least here in Austria)

On Spain it is assumed that digital accounting entries are constantly being created and removed leaving gaps in their numeration. Anyway, at the end of the year (after fiscal year closing), the accounting journal must be printed with entries numbered sequentially. So, all the Spanish accounting software I know* has a wizard to allow the renumbering of entries on a given period.

  * Some examples of such wizards:
    ContaPlus: http://www.kami.es/pub/2009-09/renumeracion_asientos/facturaplus.png
    ClassicConta: http://www.kami.es/pub/2009-09/renumeracion_asientos/classicconta.png
    ContaSol: http://www.kami.es/pub/2009-09/renumeracion_asientos/contasol.png
    Primavera: http://www.kami.es/pub/2009-09/renumeracion_asientos/primavera.png

On the Spanish localization of OpenERP we had to create a wizard to allow such renumbering, it was released as the account_renumber module available on the extra-addons.

So, for Spain:
  - Deleting account_move/account_move_lines on a non-closed fiscal year is acceptable (and usual).
  - "update_posted" is always set to true.
  - On the fiscal year closing, the accounting entries are renumbered.