what file format must my questionnaire have to upload

File format is usually not the bottleneck

Most questionnaires arrive as Excel (.xlsx), Word (.docx) or PDF, and the system recognizes all three of these without additional processing. Also, an export from a portal such as EcoVadis, Avetta or a bank's own questionnaire tool is usually supplied as PDF or Excel, and it reads the same way. With a scanned PDF — i.e. a photo of a paper questionnaire instead of a digital document — recognizing the questions takes a bit longer, but it works in most cases too.

What matters is the structure of the questions themselves, not the format of the file. A list with loose open questions about for example the number of employees or the countries where the company has establishments the system usually recognizes well. A matrix with merged cells, or a questionnaire built from dropdown menus in a portal's own layout, sometimes requires a check afterwards: the answer is then correctly in the file, but you need to verify that it ends up in the right place in the uploaded document.

What differs per format when reading

With Excel and Word, the system uses the text structure of the document itself — headings, cells, numbering — to recognize question and answer field. With PDF, this depends on whether it is a text PDF (with searchable text) or a scanned document (just an image): in the first case, recognition is as reliable as with Word, in the second case text is first converted with image recognition and an additional check is in order, especially for figures such as annual turnover or a registration number. This is not a legal requirement or standard — there is no regulation that a customer or supervisory authority sets on the file format of a questionnaire — it is purely a characteristic of how the platform itself reads documents.