Contributors mailing list archives
Re: Projects - send one invoice per customerby
Tecnativa. S. L., Pedro M. Baeza
Although my advice is you to move to v12/v13 for getting a lot of improvements in both Odoo and contract modules, meanwhile, you can migrate https://github.com/OCA/contract/tree/9.0/contract_invoice_merge_by_partner for getting a better approach IMO on contract invoicing.