Well, The simplest solution is to call your on change function in your new function for example :

@api.onchange('tax_ids'):

 def compute_tax(self):

   #Your code 

def your other function_to assign taxed(self):

discount_l.write({'tax_ids': tax_ids})

    self.compute_tax()

Hi,

Try as follows:

   discount_l.write({'tax_ids': tax_ids})
   invoice_line._onchange_price_subtotal()

invoice_id._recompute_dynamic_lines(
    recompute_all_taxes=True,
    recompute_tax_base_amount=True,
)

Thanks & Regards

Hello Odoo Learner,

Onchange method only trigger when you make any changes on field from user interface but in this case you can manually call onchange method just after writing tax as below..

discount_l.write({'tax_ids': tax_ids})
discount_l._onchange_price_subtotal()

Thanks & Regards,
Email: odoo@aktivsoftware.com
Skype: kalpeshmaheshwari