whatsapp_web_groups/change_vat_in_partner/models/account_payment.py

from odoo import models, api


class AccountPayment(models.Model):
    _inherit = "account.payment"

    @api.model_create_multi
    def create(self, vals_list):
        vals = super().create(vals_list)
        partner = self.env['account.move'].search([("name", "=", vals_list[0]["ref"])],limit=1)
        if partner:
            vals.partner_id = partner.partner_id
        return vals