Create epic fails due to custom fields


I’m working on an Excel macro to create issues and epics for a project. Issue creation works fine so far but creation of epics fails due to custom fields (epic-name and budget). Unfortunately the response is telling not too much about the error, just mentioning the field names.

That’s my JSON, what’s my mistake?

            "key": "PROJTEST"
        "summary": "testepic1",
        "description": "testepic01",
        "issuetype": {
            "name": "Epic"

JSON is OK, just had wrong ids of custom fields