Clause 7.3.10 of ISO 13485:2016 requires manufacturer „to maintain a design and development file for each medical device type or medical device family“. During audits I often come across missing design development files. This was often caused by non-compliant quality systems in the past paired with a lack of regulatory oversight. Actually it is no rocket science to retrospectively generate design development files. This can often be accomplished within a few days. Let me know if you need support.