can a colleague or advisor do this on my behalf

A colleague or adviser can do the filling in

Yes, that is possible, and in practice it often happens. The questionnaire itself does not impose any requirements as to who enters the answers or operates the client's portal. What does matter is that the content of the answers is correct and that someone within the company — usually the person responsible for it — checks them before they are submitted. Who does this checking is an internal choice, not a legal requirement.

Where the line is actually drawn: a colleague or adviser who fills in answers does so on behalf of the company. Facts such as the registration number, turnover or the number of employees must come from the chain file, not from the memory of whoever happens to be at the keyboard. If there is any doubt or unclear­ness about an answer — for example because the adviser cannot find a piece of evidence — the decision to confirm something as "yes" rests with the company itself, not with the platform and not automatically with whoever does the filling in work.

Why this is not a matter of authority

None of the sources that are relevant here — the EFRAG VSME module, the ten measures of Article 21(2) of the NIS2 Directive, or Annex A of ISO/IEC 27001 — impose any requirement as to the person who fills in a questionnaire. Those regulations are about content: what data a company records, what measures it takes, what control measures it applies. Who processes that administratively in a client's portal is an organisational choice. The same applies to data that are fixed on the basis of the Trade Register Act 2007, such as the statutory name or the registered address: those facts are publicly recorded, but who types them into a questionnaire is not reserved to anyone.