We present and compare measurements of the spacecraft potential (V_s/c) of the Rosetta spacecraft throughout its stay in the inner coma of comet 67P/Churyumov-Gerasimenko, by the Rosetta Plasma Consortium-LAngmuir Probe (RPC-LAP) and Ion Composition Analyzer (RPC-ICA) instruments. V_s/c has mainly been negative, driven by the high temperature (~5-10 eV) of the coma photoelectrons. The magnitude of the negative V_s/c traces heliocentric, cometocentric, seasonal and diurnal variations in cometary outgassing, consistent with production at or inside the cometocentric distance of the spacecraft being the dominant source of the observed plasma. LAP only picks up a portion of the full V_s/c since the two probes, mounted on booms of 2.2 and 1.6 m length, respectively, are generally inside the potential field of the spacecraft. Comparing with the minimum energy of positive ions collected by ICA, we find numerous cases with strong correlation between the two instruments, from which the fraction of V_s/c picked up by LAP is found to vary between about 0.7 and 1. We also find an ICA energy offset of 13.7 eV (95 per cent CI: [12.5, 15.0]). Many cases of poor correlation between the instruments are also observed, predominantly when local ion production is weak and accelerated ions dominate the flux, or during quiet periods with low dynamic range in V_s/c and consequently low signal-to-noise ratios.