We have to charge tax only on orders destined for Colorado and it's only 2.9%. If you have tax exempt status in the state of Colorado, please include your Colorado Sales Tax ID and a note to that effect in the comments field of your order and we'll send you a refund for the tax our cart charged you and set your customer record to tax exempt so you aren't charged in the future. If you are anywhere other than Colorado, we won't be charging you tax anyway, so we have no need for your number.