❗️ Error creating Sales Invoice: TypeError 'NoneType' and 'float' when linking advance payment

1

Hi everyone,
I’m working on a custom function to create a Sales Invoice from a Sales Order.
Here’s the basic flow:

  • Fetch the Sales Order
  • Create a Sales Invoice document
  • Map the items from the Sales Order
  • If advance payments exist, map the Payment Entry to the Sales Invoice’s advances table.

However, when I call .insert() on the Sales Invoice, I get this server error:

TypeError: unsupported operand type(s) for *: 'NoneType' and 'float'
apps/erpnext/erpnext/controllers/accounts_controller.py", line 1272, in set_advance_gain_or_loss
base_allocated_amount_in_ref_rate = advance_exchange_rate * d.allocated_amount

It seems that the advance_exchange_rate is coming as None.
I already check that the Payment Entry’s source_exchange_rate is not None and not zero before appending it to the advances.

Here’s a simplified version of the code I use for the advances part:

if sales_order_doc.advance_paid and sales_order_doc.advance_paid > 0:
    payment_entry = frappe.db.get_value("Payment Entry Reference", {
        "reference_doctype": "Sales Order",
        "reference_name": sales_order_doc.name,
        "docstatus": 1
    }, "parent")
    if payment_entry:
        payment_entry_doc = frappe.get_doc("Payment Entry", payment_entry)
        if payment_entry_doc.source_exchange_rate is None or payment_entry_doc.source_exchange_rate == 0:
            frappe.throw(f"Payment Entry {payment_entry} has an invalid or missing source_exchange_rate.")
        sales_invoice.append("advances", {
            "reference_type": "Payment Entry",
            "reference_name": payment_entry,
            "allocated_amount": sales_order_doc.advance_paid
        })

My Questions:

  • Is there something else I need to set when adding an advance manually?
  • Is there a required field like exchange_rate on the Sales Invoice Advance child table that I’m missing?
  • How should I correctly link an advance payment into a Sales Invoice programmatically?

Thanks in advance for any help!