Is there a way to tell how much a business contributes to charity?
Not easily. Look at this article:
Its data comes from a combination of surveys and public information requests to the SEC and IRS. Obviously people needed to do some work and then the validity of the info is probably debatable.
Some businesses report this in their annual report to stockholders. But I don’t know how you would verify the accuracy of what they report.
It’s a lot easier to find this for non-profits. On their 990 tax form (freely available from any non-profit, or often available online) they report how much of their funds were spent deirectly on their charitable mission.
Note that the above posts refer to publicly-traded companies. If you want to answer this question for a privately held company (e.g., Mars, Inc.), there is no way in hell.
Larger companies usually flow their charitable giving through their own foundation, which is typically funded by the corporation. You would be able to look up the foundation’s 990 online, as it’s a publicly available document, which should have information on large donations coming in.