Adequate books and records.
(6) Adequate books and records. Permanent books of account and records are maintained for as long as the costs with respect to the covered services are incurred by the renderer. Such books and records must include a statement evidencing the taxpayer's intention to apply the services cost method to evaluate the arm's length charge for such services. Such books and records must be adequate to permit verification by the Commissioner of the total services costs incurred by the renderer, including a description of the services in question, identification of the renderer and the recipient of such services, and sufficient documentation to allow verification of the methods used to allocate and apportion such costs to the services in question in accordance with paragraph (k) of this section.