Experiencing the exact same issue. Did you find any way around?

Alternatively, if I'm not mistaken you can extend the "automatic closing after", but our clients also requested to receive the invoice 1 month prior to the end of the subscription. 

Hi,

In the product form, have you tried changing the Invoicing Policy to "Prepaid/Fixed Price"?

C.

Option 1: Use Studio or Custom Code to Offset the Period Label

1. Activate Developer Mode
   Go to Settings → Activate Developer Mode.
2. Use Odoo Studio or create a custom module to override the invoice description generation logic:
   • In the model sale.subscription, the logic for label text (e.g., “3 months 01/04/2024 - 01/07/2024”) is usually built into the method that generates the invoice line description.
   • You'll need to override that method (e.g., _prepare_invoice_line) and add a 1-month offset to the dates used in the label.

Phyton Code
start_date = subscription.recurring_next_date + relativedelta(months=1)
Deploy the code or use Studio to set the computed field in the invoice line description with the adjusted label.

end_date = start_date + relativedelta(months=subscription.recurring_interval)

label = f"{subscription.recurring_interval} months {start_date.strftime('%d/%m/%Y')} - {end_date.strftime('%d/%m/%Y')}"