A dated copy of the official terms relied on, any official correspondence or notice received, proof of each payment and its stage, and the corporate resolutions if a company is sponsoring. Distinguish general web pages from individual notices addressed to the applicant.
Date every source, because the framework can change under you
The most useful habit here is unglamorous. Each time Lars reads the official page, he should save it with the date, so that later he can show what the terms were when he made a decision rather than arguing from memory. Official correspondence addressed to him personally sits in a separate category from general published guidance and should be filed accordingly.
Payment records should identify which stage each amount related to, since the nonrefundable processing fee and the post-vetting gift are distinct and are treated differently. Where the company sponsors, the corporate side needs board or shareholder resolutions authorizing the payments and recording the ongoing maintenance obligation. None of this replaces reading the current official instructions before the next step; it simply preserves the history if a question about it arises later.