35 ILCS 173/5-20
Any purchaser who does not elect the alternate tax rate to be paid to a delivering supplier shall register with the Department as a self-assessing purchaser and pay the tax imposed by Section 5-10 of this Law directly to the Department at the self-assessing purchaser rate.
A purchaser registering as a self-assessing purchaser may not revoke such registration for at least one year thereafter. Application for a certificate of registration as a self-assessing purchaser shall be made to the Department upon forms furnished by the Department and shall contain any reasonable information that the Department may require. The self-assessing purchaser shall be required to disclose the name of the delivering supplier or suppliers who are delivering the gas upon which the self-assessing purchaser will be paying tax directly to the Department.
Upon receipt of the application for a certificate of registration in proper form, the Department shall issue to the applicant a certificate of registration as a self-assessing purchaser. The applicant shall provide a copy of the certificate of registration as a self-assessing purchaser to the applicant's delivering supplier or suppliers.
35 ILCS 173/5-20