Steady-state error is a critical performance parameter in control system analysis, representing the difference between the desired output and the actual output as time approaches infinity. While steady-state error in unity feedback systems is well established, practical control systems often employ non-unity feedback due to sensor scaling, feedback conditioning, and system constraints. This paper presents a comprehensive analytical study of steady-state error in non-unity feedback control systems. Mathematical derivations for standard test inputs—step, ramp, and parabolic—are provided using the Final Value Theorem. System type classification is extended to non-unity feedback configurations, and numerical examples are included to illustrate the impact of feedback transfer functions on steady-state performance. The results demonstrate that feedback elements significantly influence error constants and must be carefully designed to meet performance specifications.