hi james 
thanks for your support 

type_id = fields.Many2one(
        string="Type", comodel_name="baba.approval.type", required=True)
    approve_amount = fields.Float('Approved Amount',compute='_compute_approve_amount')

    @api.depends('type_id')
    def _compute_approve_amount(self):
        if self.new_invoice.state == 'posted' and self.new_invoice and self.type_id == self.new_invoice.type_id:
            self.approve_amount = self.approve_amount - self.new_invoice.amount_total
def action_generate_bill(self):
    # Assuming you have necessary information for creating the invoice
    invoice_data = {
        # 'payment_reference': self.type_id.id,  # Replace with the actual partner field in your model
        # 'partner_id': self.user_id.id,  # Replace with other necessary fields
        'move_type': 'out_invoice'  # if it is an invoice otherwise in_invoice if it is a bill
        # Add more fields as needed
    }

    # Create a new invoice
    new_invoice = self.env['account.move'].create(invoice_data)

    # Find the corresponding baba.approve record based on type_id
    approve_record = self.env['baba.approval'].search([('type_id', '=', self.type_id.id)])

    # If a matching record is found, create invoice lines with adjusted amounts
    if approve_record:
        for line in new_invoice.invoice_line_ids:
            line.price_unit -= approve_record.approve_amount

    # Open the form view of the newly created invoice
    action = {
        'type': 'ir.actions.act_window',
        'res_model': 'account.move',
        'view_mode': 'form',
        'res_id': new_invoice.id,
    }

    return action
i have try this but its not wokring 
here i want from my approve_amount field of same type_Id in account.move model amount_total will be substraction when the innvoice is in posted state 

Hi Deen 

check the code following, 

assign created new_invoice record to a many2one of 'account.move'  in your model 

class MultiApproval(models.Model):
    _name = 'baba.approval'

    type_id = fields.Many2one(
        string="Type", comodel_name="baba.approval.type", required=True)
    approve_amount = fields.Float('Approved Amount',compute='_compute_approve_amount')

    @api.depends('type_id')
    def _compute_approve_amount(self):
        if self.new_invoice.state == 'posted' and self.new_invoice and self.type_id == self.new_invoice.type_id:
            self.approve_amount = self.approve_amount - self.new_invoice.amount_total

Regards