18-125-302 Me. Code R. § 2
A non-governmental entity must hold an exemption certificate or resale certificate issued by Maine Revenue Services in order to make tax-free purchases. If the State Tax Assessor determines that an applicant qualifies to make tax-free purchases, the State Tax Assessor shall issue a numbered certificate that identifies the name and address of the applicant, the tax or taxes from which it is exempt or not subject to, and the relevant exempt activity or activities. The certificate may be used by the holder only when purchasing property or services intended to be used by the holder primarily in the exempt activity or activities. When an otherwise qualifying organization is engaged in both exempt and nonexempt activities, the exemption certificate is to be issued only if the State Tax Assessor finds that the organization has adequate internal controls in place to limit the use of the certificate to exempt purchases. A decision by the State Tax Assessor to deny an application for issuance of an exemption certificate constitutes a determination of the State Tax Assessor that is subject to a petition for reconsideration pursuant to 36 M.R.S. §151.
18-125 C.M.R. ch. 302, § 2