Since 2003 the CEER has performed several cost efficiency benchmarks of electricity and gas transmission system operators (TSO(s)), the most recent being the CEER TSO Cost efficiency Benchmark 2018 (TCB18 ) study with reference year 2017 . Formally, each benchmark is procured by one of the national regulatory authorities (NRA(s)) on behalf of CEER . The purpose of these benchmark studies is to derive a static cost efficiency figure (TOTEX based) for each of the participating TSOs. . TSO benchmarking is of relevance to NRAs as European regulation stipulates that tariffs of a TSO shall reflect the actual costs incurred insofar as these costs correspond to those of an efficient and structurally comparable network operator . To follow up TCB18, CEER anticipates to start a next benchmark in 2021 referred to as the CEER TSO Cost efficiency Benchmark 2021 (TCB21) with reference year 2021.