Occasionally Paidnice will try to update an invoice in Xero (for example, to add a late fee or interest to an existing invoice) and Xero will reject the change with an error like:

Failed to send invoice - Xero Validation Error: Website must be valid

The error isn't about the invoice at all — it's about the customer contact the invoice belongs to. Xero recently tightened its validation of the Website field on contacts. Whenever any change is saved against an invoice through Xero's API, Xero now re-checks the whole contact record, including that website field, even though Paidnice hasn't touched it.

If the contact's website is stored without a protocol (e.g. www.example.com instead of https://www.example.com), or contains a typo, Xero treats it as invalid and refuses the invoice update. Contacts like this can often still be saved in the Xero web app, which is why the problem only shows up when a connected app like Paidnice tries to update one of their invoices.

This is a Xero-side issue that affects all apps connected to Xero — there's nothing to change in Paidnice itself.

1. Log in to Xero and go to Contacts, then open the customer named on the failed invoice.

2. Click Edit and find the Website field.

3. Add https:// to the start of the address (for example, change www.example.com to https://www.example.com), or correct any typo. If you don't need the website at all, simply clear the field.

4. Save the contact.

Once the contact has been corrected, Paidnice will be able to update that customer's invoices again. Any late fee or update that failed will be retried on its next scheduled run, or you can re-apply it manually from the invoice in Paidnice.

Note: If the contact's website already starts with https:// and you're still seeing this error, double-check for stray spaces or unusual characters in the field, and make sure the email addresses on the contact are valid too — Xero validates those at the same time. Still stuck? Reach out to us via chat and include the invoice number.