Error on submission: cvc-complex-type.3.2.2:Atribute 'onmousover' is not allowed to appear in element 'span'

When submitting accounts to HMRC, you may see the following error:

This happens when you tick to include review functionality when generating the iXBRL document (as this is not intended for electronic filing purposes).

To resolve this, generate the iXBRL again and ensure that the review functionality option remains unticked: