Why do I need to send the Customer ID in the Create Purchase Order Request?

I'm trying to create a purchase order using this endpoint https://www.zoho.com/inventory/api/v1/purchaseorders/#create-a-purchase-order

Unfortunately, I'm getting this error

{
    "code": 4,
    "message": "Invalid value passed for Customer ID"

}

The doc doesn't mention anything about Customer ID.

How can I fix it?

This is the payload

{
    "purchaseorder_number": "20240902aaaaa",
    "date": "2024-09-02",
    "delivery_date": "2024-09-20",
    "exchange_rate": 1,
    "template_name": "Standard Template",
    "total": 0,
    "attention": "",
    "vendor_name": "DB#1",
    "line_items": [
        {
            "name": "PU23888H",
            "quantity": 1800,
            "description": "[36PCS] SIZES 1-2-2-2-2-2-1 [3/26-5/27-7/28-9/29-11/30-13/31-15/32] \tJuniors/ \t DARK WASH HIGH RISE MISSY BLING EMBROIDERY BOOTCUT"
        }
    ]

}