Objective: The aim of this study was to report the accuracy of hearing aid fittings 1) before and after clinical attempts to match prescribed targets (‘REM-adjustments’), and 2) after opportunities for fine-tuning. Design: A prospective audit of real-ear-insertion gain (REIG) measurements made during routine hearing aid fitting and follow-up appointments. REIG measurements were compared to prescribed targets. Sample: Two groups of new hearing aid users: 1) 46 patients attending a hearing aid fitting (age 27 – 96), 2) 45 patients attending a hearing aid follow-up (age 27 – 93). Results: Fitting group: The over- and under- amplification measured before REM-adjustment reached 19 dB and 17 dB SPL respectively. The proportion of fittings meeting recommended gain criteria significantly increased after REM-adjustments (22% vs 74%, McNemar’s test p < .0005). Follow-up group: The proportion of fittings within recommended criteria was significantly lower at follow-up than at the REM-adjusted fitting (24% vs 53%, McNemar’s test, p <= .004). Conclusions: Routine clinical processes increased the proportion of fittings which met recommended gain criteria and reduced the range of over- and under-amplification observed prior to REM-adjustments. Measurements made at follow-up appointments found the accuracy achieved at hearing aid fittings was not maintained.