Hi,

You can make the total_balance as compute field depending on the field total_inquiry and early_balance field you mentioned.

@api.depends('total_inquiry', 'early_balance')
def _compute_total_balance(self):
    balance = self.early_balance + self.total_inquiry
    self.total_balance = balance

total_balance = fields.float(string='Total Balance', compute=_compute_total_balance)

The above code is based on new API, you might have to adjust the code according to old API.

Thanks