Tax Exempt Status Verfication web service

I'm looking for an online web service that verifies tax exempt status by tax id so that I can incorporate thi开发者_运维技巧s business logic into the compute_total_price procedure.

What web services or methods do other e-commerce sites use to accommodate to the tax exempt organizations?

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These guys have something that can do this. They look to be somewhat pricey. http://www2.guidestar.org/. In particular, their Web Services is under custom solutions, and the price is "contact us".

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I searched a few years back and recall not having found anything useful.

I ended up adding applicable taxes where appropriate unless a flag was set in the user's profile. The latter was set by the site's owner after (manually) verifying that customers are indeed tax exempt.