This seems to be an internal matter of the partner and not EU regulations.
The expense needs to be actual, necessary and economic to be allowed by EU – and in accordance with the normal accounting procedures of the partner. Internal accounting departments have their own rules which override the EU regulations, especially where they are more “harsh”. If the University normally accepts invoices in professors or researchers names and it can be demonstrated that they are for the project, the EU will normally accept the cost (especially where it is not “material” in relation to the overall cost of the project). Remember, however, that VAT and taxes – even of another member State, such as on hotel and restaurant bills – are not allowable.
Incidentally we have seen many cases where an employer will not accept the cost of alcoholic beverage, even on a restaurant or hotel bill, and therefore nor will the EU for that partner. Normal accounting procedures for the organization (subject to the expense not being an in-eligible cost, as defined by EU) override all else.