The Montshire Museum is a 501(c)(3) nonprofit organization. The value of membership benefits is not substantial so membership fees are fully tax-deductible as provided by law. Some donor benefits, including guest admission passes, have a substantial value and reduce the tax-deductible amount of your gift. Refer to your gift acknowledgement letter or read a detailed description of membership levels, benefits, and their impact on tax deductibility. Benefits and tax deductibility 2015.