http://www.kenniffonline.com/disgorgement-of-profits/

Why don’t churches have to pay taxes on their income (tithes)?
Given that taxes help, or at least are supposed to help, the common good, why are churches the only ones that don’t? And I dispute they are non-profit organizations. They’re selling stuff. Truly. Ca-ching. Those stained glass windows aren’t cheap. Wouldn’t all the poor babbys benefit from the Vatican’s disgorgement of loot?
Any non-profit can be exempt from taxes. For instance, our hang gliding club has non-profit status. However, churches go a step beyond that. They are considered charitable organizations, such that money contributed to it is considered a charitable, tax deductible contribution.
Even if a church only spends the money you give it on a lovely edifice and uses the remainder to convert new followers, this is considered charitable work.