Can someone please confirm the Invoice API works to get these fields?

I am following the API documentation (https://www.zoho.com/books/api/v3/invoices/#get-an-invoice) to write a custom function. I am able to get a lot of fields but having a problem with the following two:

invoice.get("payment_made");//returning null but payments have been made to my test invoice

invoice.get("is_inclusive_tax");//returning null and I am expecting true or false

As an example, the following is one that's working for me

invoice.get("discount").toDecimal();

Any help is greatly appreciated!