This is a multicenter, randomized, double-blind, parallel-group study to evaluate the efficacy and safety of the addition of UMEC (62.5 microgram[mcg]) when administered once-daily via dry powder inhaler (DPI) to Inhaled corticosteroid/ Long-acting beta2-agonist (ICS/LABA) twice-daily compared with placebo via DPI added to the ICS/LABA therapy over a treatment period of 12 weeks in subjects with COPD. This study is designed to investigate the addition of UMEC to ICS/LABA combinations at approved doses and frequencies for the treatment of COPD including SERETIDE™ 500/50 mcg twice daily, Fluticasone Propionate/Salmeterol Combination (FSC) 500/50 twice daily generic products such as AIRFLUSAL FORSPIRO inhaler 500/50 mcg twice daily or ROLENIUM ELPENHALER inhaler 500/50 mcg twice daily and SYMBICORT TURBUHALER inhaler at doses of 200/6 mcg twice daily and 400/12 mcg twice daily, over 12 weeks in subjects with COPD. Albuterol/salbutamol metered-dose-inhaler (MDI) or nebules will be issued throughout the study for use as-needed (prn).