Overview
When syncing orders or invoices from Ordermentum to Xero, you may see error messages that prevent the sync from completing.
Each error points to a specific issue that must be resolved before the invoice can successfully sync to Xero.
This guide explains:
Why does a specific Xero sync error occurs
How to fix the issue in Ordermentum or Xero
When a manual update in Xero is required
Before You Begin
Make sure you have:
Access to the Supplier Dashboard in Ordermentum
Permission to edit orders or venue details
Access to Xero settings, including products, account codes, or Business Settings (depending on the error)
⚠️ If an invoice is already marked as Paid in Xero, it is locked. Any changes must be made manually in Xero.
1. Sync unsuccessful. Please try to resync
Error message in Ordermentum: Sync unsuccessful. Please retry sync. If problem persists, please contact support.
Why this happens
This is a generic error returned by Ordermentum or Xero. It may be caused by:
A temporary timeout
A backend delay
An account-level syncing issue
How to fix it
Manually re-sync the invoice in Ordermentum.
If the error continues, contact Ordermentum Support.
💡 Access this article to help you manually resync an invoice to Xero.
2. This document cannot be edited as it has a payment or credit note allocated to it.
Error message in Ordermentum: This document cannot be edited as it has a payment or credit note allocated to it.
Why this happens
Xero returns this error when the synced invoice has:
A payment, or
A credit note applied
Once this happens, the invoice can no longer be edited via sync.
How to fix it
Apply any required changes manually in Xero
ℹ️ This error does not necessarily mean there is a mismatch between Ordermentum and Xero. Any change in Ordermentum will still attempt a sync and may surface this message again.
3. No items available to sell
Error message in Ordermentum: A validation exception occurred, <product name> No items available to sell.
Why this happens
This occurs when:
You are using tracked inventory in Xero, and
There isn’t enough stock available to fulfil the order
How to fix it
Update stock levels in Xero, or
Disable tracked inventory for the affected item in Xero
4. Account/Tax Rate must be Valid
Error message in Ordermentum: A validation exception occurred – Account must be valid. Tax rate must be valid.
Why this happens
The sales code sent from Ordermentum does not match an active account code in Xero.
This can happen at the:
Product level
Variant level
How to fix it
Check the sales code on the product or variant in Ordermentum.
Confirm the same code exists and is active in Xero.
Update the product if needed.
Edit and save the order so the updated code is sent.
Manually re-sync the invoice.
💡 Access this article to help you manually resync an invoice to Xero.
Product sales code in Ordermentum:
Product sales account code in Xero:
5. Invoice not in a valid status for modification
Error message in Ordermentum: A validation exception occurred, Invoice not of valid status for modification.
Why this happens
Xero returns this error when the invoice is:
Awaiting payment
Linked to a payment
Deleted or voided
These invoices prevent updates via sync.
How to fix it
Make changes manually in Xero
ℹ️ Seeing this error does not automatically mean data is out of sync. Ordermentum will still attempt to sync whenever changes occur.
6. A validation exception occurred. Invoice # must be unique
Error message in Ordermentum: A validation exception occurred, Invoice # must be unique.
Why this happens
This error can occur if:
A manual invoice exists in Xero with the same invoice number, or
Two Ordermentum supplier accounts are connected to the same Xero organisation
How to fix it
Update the invoice number directly in Xero
If you have multiple supplier accounts connected to one Xero account:
Contact Ordermentum Support
Request a change to the default invoice prefix for one supplier
7. A validation exception occurred. Item code is not valid
Error message in Ordermentum: A validation exception occurred, Item code <item code> is not valid.
Why this happens
The item code in Ordermentum does not match the item code in Xero. This may happen if:
A product was renamed
An item was deleted
Codes were edited in one system only
How to fix it
Update the item code in Ordermentum or Xero so they match.
Manually re-sync the invoice.
If the issue persists, contact support.
💡 Access this article to help you manually resync an invoice to Xero.
8. The UnitAmount field is mandatory and cannot be derived from the Quantity and LineAmount fields
Error message in Ordermentum: A validation exception occurred, The UnitAmount field is mandatory and cannot be derived from the Quantity and LineAmount fields., The LineAmount field is mandatory and cannot be derived from the Quantity and UnitAmount fields.
Why this happens
This error occurs when the order does not have a delivery date.
Xero requires a delivery date to calculate invoice values correctly.
How to fix it
Add a delivery date to the order.
If unpaid: edit the order directly
If paid: update the delivery date via the Order List view
Manually re-sync the invoice.
💡 Access this article to help you manually resync an invoice to Xero.
9. A validation exception occurred, The TaxType code 'OUTPUT' cannot be used with account code
Error display in Ordermentum: A validation exception occurred, The TaxType code ‘OUTPUT’ cannot be used with account code ‘<account code>’.
Reason: This usually happens when a product is linked to an incorrect sales account code in Xero. Xero doesn’t allow the OUTPUT tax type to be used with that particular account, so the invoice is blocked from syncing.
Resolution: Check the product’s settings in Ordermentum and make sure a valid sales code is assigned. That sales code must match an active and compatible account code in Xero.
Once updated:
Edit and save the order to trigger a sync, or
Manually re-sync the invoice to push the changes through
💡 Access this article to help you manually resync an invoice to Xero.
Need more help?
If you’re still seeing errors or aren’t sure how to fix one:
Use the Help chat in the bottom-right corner of the Ordermentum app
Or email support@ordermentum.com
Our team can help review the error and guide you through the next steps.