Example request

{
  "matter_ref": {
    "id": "00000000-0000-0000-0000-000000000000"
  },
  "item_ref": {
    "id": "00000000-0000-0000-0000-000000000000"
  },
  "billed_by_user_ref": {
    "id": "00000000-0000-0000-0000-000000000000"
  }
}