Accounting and managing in-kind contributions is one of the hardest things that a research centre manager has to do. There's no easy solution - but you could try regular updates in meetings.
Just finished doing the webinar on financial management and budget setting for researchers.
One of the questions that came up was "How do you account for in-kind particularly into the future not so much into the past?".
One of the ways that I've found that works for me is to set up a regular meeting. Whether that be quarterly with your exec team, the people that are providing the in kind, and have a standing item that basically questions them on have they provided the amount of in-kind that they said they would. So that serves as a reminder to them that they need to be providing the in-kind, but also it serves as a trigger for have they provided it, and then an actionable, and definitive source of information is yes, they have provided the in-kind. That's often a sufficient evidence for say a granting body who is matching that in-kind with some kind of cash contribution.
Hope that helps.