Sorry, mildly off topic but had to jump in here to add additional information. IKEA is the worlds largest charity in terms of cash it's sitting on, but it is not the worlds largest in terms of what it gives away. In 2007 it only gave away 1.3million euros, despite sitting on 31billion and earning far more. The stores also still pays between 700million and 1billion to the founding family. lastly the money it does give away is for the furtherment of architecture.
I always took it as read that it's a charity because of the tax arrangements (i.e. if they didn't benefit from setting it up that way, they wouldn't be a charity at all).
"IKEA" is a network of many different companies. Some of them are registered as nonprofits (not charities) as a tax optimization which is probably what you are remembering. There is also the charitable organization that was mentioned above but afaik that's not for tax purposes.
So while it may be large, I don't think we can let it off the hook of its tax arrangements, just because it's a charity. http://www.mentalfloss.com/blogs/archives/14675