HI Juan Muñoz,

The invoice number is auto generated number and which is read-only.

Its the standard process its not editable otherwise anyone can change the number to any and sequence may be different.

Just revert your changes in which you made in base module it will no affect to your current database.

If your current invoice made for wrong customer than just cancel it and reuse it for another customer it will use the same sequence as it is already generated.

Regarding change the sequence number for newly created invoice.

That you can update from settings under the sequence.

For Recovery : Just revert back the changes which made in base module and upgrade the account module.

If you are not able to upgrade module from screen than

Upgrade it from terminal by applying -d database and -u module_name.

Hope this will help.

Rgds,

Anil.

actually i didnt understand your question, i will gave you two links to refer that you can make chances of your invoices http://www.odoo.yenthevg.com/change-invoice-numbering-odoo-8/

https://www.odoo.com/forum/help-1/question/changing-invoice-sequence-numbering-to-include-customer-reference-17213