I am trying to onchange sale.order.line 's field (tax_id) and update sale.order 's field, is that even possible? I had tried:

value = {
    'price_unit': '' ,
    'x_istaxcode': True       #custom field in sale.order (boolean)
}
return {'value': value}

Output:

price_unit of the sale order line become 0.00.

x_istaxcode is not changing.

Please advise.