At a previous company I found an internal excel document with everyone's salary, from the CEO down to his assistant. On the doc my salary was inflated ~25K to what my actual gross was, I can only assume these perks/benefits were included on top of the salary. But it shows they see that on paper that's how they saw my salary hit. I think it would be wise to include these in your previous "salary".

I never did find any more details on the document though :(

There was a post on hacker news a few months ago that explained exactly this. I believe it's a fair way of calculating it (if you feel that you must disclose something for whatever reason).