Getting error "Customer is required" when sending a POST request to RMAProcSvc/SelectedSerialNumbers, but there is no Customer field

I’m trying to add a serial number to an RMA under the Details → Detail tab via the API. I’m using RMAProcSvc/SelectedSerialNumbers and sending a POST request. This is my payload:

{Company: "SIE", SerialNumber: "111117", PartNum: "S-Evaluation"}

And this is the response:

        "HttpStatus": 400,
        "ReasonPhrase": "REST API Exception",
        "ErrorMessage": "Customer is required.",
        "ErrorType": "Ice.Common.BusinessObjectException",
        "ErrorDetails": [
                "Message": "Customer is required.",
                "Type": "Error",
                "Table": "RMAHead",
                "Program": "Epicor.RESTApi.dll",
                "Method": "ThrowUpdateExtException",
                "ColumnNumber": 17,
                "LineNumber": 40

This is the template for the payload:

  "Company": "SIE",
  "SerialNumber": "string",
  "Scrapped": true,
  "ScrappedReasonCode": "string",
  "Voided": true,
  "Reference": "string",
  "ReasonCodeType": "string",
  "ReasonCodeDesc": "string",
  "PartNum": "string",
  "SNPrefix": "string",
  "SNBaseNumber": "string",
  "SourceRowID": "00000000-0000-0000-0000-000000000000",
  "TransType": "string",
  "PassedInspection": true,
  "Deselected": true,
  "KitWhseList": "string",
  "RawSerialNum": "string",
  "KBLbrAction": 0,
  "KBLbrActionDesc": "string",
  "PreventDeselect": true,
  "XRefPartNum": "string",
  "XRefPartType": "string",
  "PreDeselected": true,
  "poLinkValues": "string",
  "SNMask": "string",
  "NotSavedToDB": true,
  "SysRowID": "00000000-0000-0000-0000-000000000000",
  "RowMod": "string"

It lets me add the serial number in the UI, but not the API. Does anyone have any idea how to solve this? Thanks!

OData methods tend to list all service tables when some of them are not meant to be modified directly.

I would suggest to see the flow of calls in the browser’s developer tools, or a classic UI trace and use the api Custom Methods.