Creating an Invoice with transaction level discount using REST API

Hi

I am using the rest api to create invoices on netsuite but I can’t figure out how to push a header level discount in the request. The fields in the Netsuite UI is discount Rate, which I can edit manually on the UI per order but I want to do this through REST.

This is the field I want to target: https://i.imgur.com/eGRSlyB.png

I’ve tried setting the discount rate manually and then querying that invoice to see if I can see the field for discount rate in the response but it’s missing.

Would appreciate any help on this.

Things I’ve tried:
"discountItem": { "id": <itemID> },
"discountRate": -12.00

but I get back:

{

"type": "https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.1",

"title": "Bad Request",

"status": 400,

"o:errorDetails": [

{

"detail": "Unknown field name 'discountItem'. The field does not exist on this record instance.",

"o:errorPath": "discountItem",

"o:errorCode": "NONEXISTENT_FIELD"

}

]

}