A bstract. We present DECO (“Discrete and Efficient Counting of Operators”), an implementation of the Hilbert series to enumerate subleading operator bases for SMEFT-like EFTs with symmetry groups as typically found in flavour and BSM physics. DECO can accommodate EFTs with arbitrary numbers and combinations of the SM gauge groups, as well as the discrete groups S4 , A4 , and ?n, and U(1) groups with residual global charge (and these groups’ most important representat...