from odoo import _, api, fields, models class ProjectTask(models.Model): _inherit = "project.task" funder_ids = fields.One2many("project.funder", "task_id", string="funder") amount_total = fields.Float(compute="_compute_amount_total", string="Amount Total") @api.depends("funder_ids") def _compute_amount_total(self): for record in self: record.amount_total = sum(record.funder_ids.mapped("amount"))