Which is very far from saying the accounts have not been signed off. Stating they have not been signed off is in fact a lie.
European Commission - PRESS RELEASES - Press release - EU accounts signed off, but errors persist in all main spending areas, say EU Auditors
6.2 billion equates to around 4% of the budget.
In addition most, if not all of the "error rate" as the auditor puts it, is down to national governments and / or the organisations that receive the funding, not the EU itself.