Private entities are permitted to use any written terms and conditions between the parties 鈥� without regard to their legal enforceability 鈥� to identify, classify and account for common control leases. In addition, all lessees (public or private), in general, amortize leasehold improvements related to a common control lease over their 鈥榰seful life鈥� to the common control group 鈥� regardless of the ASC 842 鈥榣ease term鈥� 鈥� as long as they continue to control the use of the underlying leased asset.