EinS is a Mathematica package allowing one to perform operations with indexed objects, which may or may not be tensors. The main application field of EinS is computations with indexed objects involving implicit (Einstein) summations (EinS stands for ”Einstein Summation handler”). The idea of the package was to create a simple (EinS is a relatively small package consisting of approximately 3000 lines of code), flexible package which would be easy to alter for solving any problem involving indexed objects and which would not waste time for doing anything we do not ask it to do (the latter is usual fate of the users of too general software). On the other hand, package works under Mathematica which is one of the most advanced and flexible computer algebra systems. This allows the user to employ all the power of Mathematica for solving his problem. In order to work with EinS user should have basic knowledge of the Mathematica’s control structures and language. Computer algebra system (CAS).