How to post starting balance on an EU invoice?

Following the (ongoing?) change to how the reverse charge is handled, I’m not sure how the API wants me to post a contact’s balance on an invoice.

This is the situation: I want to create an invoice in FreeAgent for an EU contact. The contact has a balance. The invoice has several items which are sales and one item which represents the contact’s balance.

I know how to post the sales invoice items. However since the reverse charge change I’m not sure how to post the balance. This is what I tried to do but doesn’t work:

    "invoice": {
        "ec_status": "Reverse Charge",
        "invoice_items": [
                "price": -12.34,
                "quantity": 1,
                "description": "Applied balance",
                "sales_tax_status": "EXEMPT"

The validation error says that the sales_tax_rate must be 0% for reverse charge invoices.

However to my mind a balance is not something that’s in or out of scope of VAT; it’s just a balance. That’s why I marked it as exempt.

Please could you tell me how I should adjust this invoice item?

Many thanks,
Andrew Stewart

My code retried the JSON every 30 minutes and I can see that it was accepted and the invoice created at around 11:37:50 on 25.11.2022.

Presumably you (FreeAgent) changed something on your end – thank you!