I am creating invoices programmatically in Odoo12 all everything is going well but there is a problem in invoice which is partially paid i.e. In-Payment because its residual ​is not calculating.

I am trying to calculate Amount Due but all nothing happened. While creating invoice I am assigning value to 

Example:

self.env['account.invoice'].create({

'residual': my_balance_field

})

Any help, any guidance?