Avoid increase of invoice number if order is canceled

Hello Ciroxxx,
This doesn’t require any coding, it’s a simple matter of setting the attachment settings (General settings tab). First to check is that you don’t have the ‘Admin New Order email’ enabled. This email is sent out for orders that are cancelled later too.
I actually recommend to attach it only to the Completed and Invoice emails (the latter is a manual email). That should prevent any premature invoice creation.

Hope that helps!

Ok, just applied settings you suggested.
Now I just need to hide, in the woocommerce order panel, the create pdf icon for canceled orders, to avoid wrong clicks and consequently messed up invoices numbers.
Did you provide some filters?

Yes! Check this thread:
https://www.ads-software.com/support/topic/disable-invoice-function/#post-6219452

Hi.
I try to do this in General setting tab, but the system continue to generate Invoice and Receipt on the canceled order. It doesn’t avoid increase of invoice number. Can you help me, please? Thanks in advance.

Since you mention a ‘Receipt’, this may actually be caused by the plugin that creates these receipts. This explains when invoice numbers are assigned:
Invoice numbers explained.
Note that the BUTTON will always be visible in the admin, regardless of whether an invoice was created. If you then click this button, the invoice number will be created.

Ewout

OK. So will the invoice number be created only when the button in the order window is clicked?

Correct! (assuming that you have disabled all attachment options)